<?xml version="1.0" encoding="UTF-8"?>
<!--

Documentation for LCL (Lazarus Component Library) and LazUtils (Lazarus 
Utilities) are published under the Creative Commons Attribution-ShareAlike 4.0 
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Copyright (c) 1997-2023, by the Lazarus Development Team.

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<fpdoc-descriptions>
<package name="lcl">
<!--
====================================================================
LazCanvas
====================================================================
-->
<module name="LazCanvas">
<short>
Classes and functions for extending TFPImageCanvas.
</short>
<descr>
<p>
<file>lazcanvas.pas</file> contains classes and functions for extending 
TFPImageCanvas to support more stretching filters, and to support all 
features from the LCL TCanvas. TLazCanvas also fixes various small problems 
and incompatibilities between TFPImageCanvas versions, making the interface 
smoother and more consistent.
</p>
<p>
Do not use anything from the <b>LCL</b> here, as this unit should be kept 
strictly independent. <file>LCLProc.pas</file> is allowed for DebugLn, but 
only during debugging or profiling.
</p>
<p>
Author: Felipe Monteiro de Carvalho
</p>
</descr>

<!-- unresolved external references -->
<element name="Classes"/>
<element name="SysUtils"/>
<element name="Contnrs"/>
<element name="Math"/>
<element name="fpimgcanv"/>
<element name="fpcanvas"/>
<element name="fpimage"/>
<element name="clipping"/>
<element name="pixtools"/>
<element name="fppixlcanv"/>
<element name="IntfGraphics"/>
<element name="LazRegions"/>
<!-- used for debugging or profiling -->
<element name="LazSysUtils"/>
<element name="LCLProc"/>

<element name="TLazCanvasImageFormat">
<short>Identifies image formats supported in TLazCanvas.</short>
<descr>
<p>
Used in the implementation of the <var>CanvasCopyRect</var> method in 
<var>TLazCanvas</var>, and in custom-drawn LCL controls to speed up image 
drawing in the LCL interface.
</p>
</descr>
<seealso>
<link id="TLazCanvas.CanvasCopyRect"/>
</seealso>
</element>
<element name="TLazCanvasImageFormat.clfOther">
<short>Images use a format other than those in this enumeration.</short>
</element>
<element name="TLazCanvasImageFormat.clfRGB16_R5G6B5">
<short>Images use 16-bit RGB colors.</short>
</element>
<element name="TLazCanvasImageFormat.clfRGB24">
<short>Images use 24-bit RGB colors.</short>
</element>
<element name="TLazCanvasImageFormat.clfRGB24UpsideDown">
<short>Images use 24-bit RGB colors with inverse values.</short>
</element>
<element name="TLazCanvasImageFormat.clfBGR24">
<short>Images use 24-bit BGR colors.</short>
</element>
<element name="TLazCanvasImageFormat.clfBGRA32">
<short>Images use 32-bit BGR colors with an Alpha channel.</short>
</element>
<element name="TLazCanvasImageFormat.clfRGBA32">
<short>Images use 32-bit RGB colors with an Alpha channel.</short>
</element>
<element name="TLazCanvasImageFormat.clfARGB32">
<short>
Images use 32-bit RGB colors with an Alpha channel in the low-order octet.
</short>
</element>

<element name="TFPSharpInterpolation">
<short>Implements a very sharp and square interpolation.</short>
<descr>
<p>
TFPSharpInterpolation implements a very sharp and square interpolation for 
stretching, similar to StretchBlt from the Windows API.
</p>
</descr>
<seealso/>
</element>

<element name="TFPSharpInterpolation.Execute">
<short>
Paints an image on the Canvas using the specified coordinates and dimensions.
</short>
<descr/>
<seealso/>
</element>
<element name="TFPSharpInterpolation.Execute.x">
<short>Horizontal coordinate.</short>
</element>
<element name="TFPSharpInterpolation.Execute.y">
<short>Vertical coordinate.</short>
</element>
<element name="TFPSharpInterpolation.Execute.w">
<short>Width for the output.</short>
</element>
<element name="TFPSharpInterpolation.Execute.h">
<short>Height for the output.</short>
</element>

<element name="TLazCanvasState">
<short>Contains properties reflecting the state for a Lazarus canvas.</short>
<descr>
<p>
<var>TLazCanvasState</var> is a class with public members that reflect the 
state for a <var>TLazCanvas</var> instance. A destructor is provided to 
ensure that resources allocated to members variables are freed before the 
class instance is destroyed.
</p>
<p>
Instances of <var>TLazCanvasState</var> are created, stored, and retrieved 
using an internal list in <var>TLazCanvas</var> in its <var>SaveState</var> 
and <var>RestoreState</var> methods.
</p>
</descr>
<seealso>
<link id="TLazCanvas.SaveState"/>
<link id="TLazCanvas.RestoreState"/>
<link id="TLazCanvas.AssignedBrush"/>
<link id="TLazCanvas.AssignedFont"/>
<link id="TLazCanvas.AssignedPen"/>
<link id="TLazCanvas.BaseWindowOrg"/>
<link id="TLazCanvas.WindowOrg"/>
</seealso>
</element>

<element name="TLazCanvasState.Brush">
<short>Brush for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvasState.Pen">
<short>Pen for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvasState.Font">
<short>Font for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvasState.BaseWindowOrg">
<short>Base window origin for the canvas.</short>
<descr>
<p>
The values in <var>WindowOrg</var> are relative to the coordinates in 
<var>BaseWindowOrg</var>. BaseWindowOrg coordinates are relative to the 
canvas for the containing Form. It is useful when implementing the non-native 
windowed controls.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvasState.WindowOrg">
<short>Window origin for the canvas.</short>
<descr>
<p>
Contains the absolute coordinates for the canvas with 
<var>BaseWindowOrg</var> summed up.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvasState.Clipping">
<short>Indicates if Clipping is enabled for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvasState.ClipRegion">
<short>Defines the clipping region for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvasState.Destroy">
<short>Destructor for the class instance.</short>
<descr>
<p>
<var>Destroy</var> is the overridden destructor for the class instance. 
Destroy ensures that resources allocated for the <var>Brush</var> and 
<var>Pen</var> properties are freed before the class instance is destroyed. 
Destroy calls the inherited destructor prior to exiting from the method.
</p>
</descr>
<seealso>
<link id="TLazCanvasState.Brush"/>
<link id="TLazCanvasState.Pen"/>
</seealso>
</element>

<element name="TLazCanvas">
<short>
Implements a canvas which masks differences between FCL and LCL canvas 
classes.
</short>
<descr>
<p>
<var>TLazCanvas</var> is an FCL <var>TFPImageCanvas</var> descendant. 
TLazCanvas extends the ancestor class to support stretching filters and 
features found in the <var>TCanvas</var> class from the LCL. TLazCanvas also 
fixes various small problems and incompatibilities between 
<var>TFPImageCanvas</var> versions, making the interface smoother and more 
consistent.
</p>
<p>
TLazCanvas is used in the implementation of custom-drawn widgetset classes, 
and provides a device context used to perform drawing operations for a 
control.
</p>
<p>
There are several useful examples using TLazCanvas on the Lazarus Wiki at:
</p>
<p>
<url href="https://wiki.freepascal.org/Developing_with_Graphics">
Developing with Graphics
</url>
</p>
</descr>
<seealso>
<link id="#lcl.graphics.TCanvas">TCanvas</link>
</seealso>
</element>

<element name="TLazCanvas.FAssignedBrush"/>
<element name="TLazCanvas.FAssignedFont"/>
<element name="TLazCanvas.FAssignedPen"/>
<element name="TLazCanvas.FBaseWindowOrg"/>
<element name="TLazCanvas.PolygonNonZeroWindingRule"/>
<element name="TLazCanvas.FLazClipRegion"/>
<element name="TLazCanvas.FWindowOrg"/>

<element name="TLazCanvas.GraphicStateList">
<short>Stores saved canvas state information.</short>
<descr>
<p>
Used to store and restore canvas states in the <var>SaveState</var> and 
<var>RestoreState</var> methods. Contains <var>TLazCanvasState</var> class 
instances.
</p>
</descr>
<seealso>
<link id="TLazCanvasState"/>
<link id="TLazCanvas.SaveState"/>
<link id="TLazCanvas.RestoreState"/>
</seealso>
</element>

<element name="TLazCanvas.GetAssignedBrush">
<short>Gets the value for the AssignedBrush property.</short>
<descr/>
<seealso>
<link id="TLazCanvas.AssignedBrush"/>
</seealso>
</element>
<element name="TLazCanvas.GetAssignedBrush.Result">
<short>Value for the AssignedBrush property.</short>
</element>

<element name="TLazCanvas.GetAssignedPen">
<short>Gets the value for the AssignedPen property.</short>
<descr/>
<seealso>
<link id="TLazCanvas.AssignedPen"/>
</seealso>
</element>
<element name="TLazCanvas.GetAssignedPen.Result">
<short>Value for the AssignedPen property.</short>
</element>

<element name="TLazCanvas.GetAssignedFont">
<short>Gets the value for the AssignedFont property.</short>
<descr/>
<seealso>
<link id="TLazCanvas.AssignedFont"/>
</seealso>
</element>
<element name="TLazCanvas.GetAssignedFont.Result">
<short>Value for the AssignedFont property.</short>
</element>

<element name="TLazCanvas.GetWindowOrg">
<short>Gets the value for the WindowOrg property.</short>
<descr/>
<seealso>
<link id="TLazCanvas.WindowOrg"/>
</seealso>
</element>
<element name="TLazCanvas.GetWindowOrg.Result">
<short>Value for the WindowOrg property.</short>
</element>

<element name="TLazCanvas.SetWindowOrg">
<short>Sets the value for the WindowOrg property.</short>
<descr/>
<seealso>
<link id="TLazCanvas.WindowOrg"/>
</seealso>
</element>
<element name="TLazCanvas.SetWindowOrg.AValue">
<short>New value for the WindowOrg property.</short>
</element>

<element name="TLazCanvas.SetColor">
<short>Sets the color for the pixel at the specified coordinates.</short>
<descr/>
<seealso/>
</element>
<element name="TLazCanvas.SetColor.x">
<short>Horizontal pixel coordinate.</short>
</element>
<element name="TLazCanvas.SetColor.y">
<short>Vertical pixel coordinate.</short>
</element>
<element name="TLazCanvas.SetColor.AValue">
<short>Color for the pixel.</short>
</element>

<element name="TLazCanvas.DoCreateDefaultFont">
<short>Creates the custom font used as the default for the canvas.</short>
<descr>
<p>
<var>DoCreateDefaultFont</var> is an overridden <var>TFPCustomFont</var> 
function used to provide the default font for the canvas class instance. 
DoCreateDefaultFont implements the abstract virtual method defined in an 
ancestor class, and emulates the method defined in TCanvas.
</p>
<p>
DoCreateDefaultFont sets the <var>Size</var> property in the font to zero 
(<b>0</b>); this causes the default font size for the platform or widget set 
to be used. The <var>FPColor</var> property in the font is set to 
<var>colBlack</var>.
</p>
</descr>
<seealso/>
</element>
<element name="TLazCanvas.DoCreateDefaultFont.Result">
<short>TFPCustomFont instance created and initialized in the method.</short>
</element>

<element name="TLazCanvas.DoRectangle">
<short>
Adjusts the fcl-image coordinate system to be compatible with coordinates 
used in TCanvas.
</short>
<descr>
<p>
Adjusts the values in <var>Bounds</var> to use the coordinate system in 
<var>TCanvas</var>, and draws borders using the style and/or pattern in the 
Pen for the canvas.
</p>
<p>
<var>DoRectangleFill</var> is used to optimize and fill a rectangle area.
</p>
</descr>
<seealso>
<link id="TLazCanvas.DoRectangleFill"/>
</seealso>
</element>
<element name="TLazCanvas.DoRectangle.Bounds">
<short>TRect with the bounds for the rectangular area.</short>
</element>

<element name="TLazCanvas.DoRectangleFill">
<short>
Adjusts the FCL image rectangle to be LCL compatible and draws a filled 
rectangle on the canvas.
</short>
<descr>
<p>
<var>DoRectangleFill</var> adjusts the fcl-image coordinate system to be 
compatible with coordinates used in <var>TCanvas</var>.
</p>
<p>
It calls the FCL SortRec routine (in <file>clipping.pp</file>) to normalize 
the values in Bounds prior to the drawing operation. It also shrinks the 
rectangle by a single pixel on the bottom and right edges for the border drawn 
in the Rectangle method. The original values in Bounds are not changed though 
- a temporary copy of Bounds is used in the method.
</p>
<p>
Values in Brush, like the Color and Style properties, are used to draw the 
filled rectangle. Style determines the routine(s) called to fill the drawing 
area as follows:
</p>
<dl>
<dt>bsSolid</dt>
<dd>
Fills the specified area with the Brush color. If the rectangle covers the 
entire width and height for the canvas and Clipping is not enabled, the 
FillColor method is used. Otherwise, the FillRectangleColor method is called 
using the adjusted bounds for the canvas.
</dd>
<dt>bsPattern</dt>
<dd>
Calls FillRectanglePattern to fill the rectangle with the pattern specified 
for the Brush.
</dd>
<dt>bsImage</dt>
<dd>
Fills the rectangle with the image assigned to the Brush. Uses 
RelativeBrushImage to determine whether FillRectangleImageRel or 
FillRectangleImage is called for the operation. A PixelCanvasException 
exception is raised for the style if an image has not been assigned in Brush.
</dd>
<dt>bsBDiagonal</dt>
<dd>
Calls FillRectangleHashDiagonal to fill the rectangle using the size for the 
hash pattern.
</dd>
<dt>bsFDiagonal</dt>
<dd>
Calls FillRectangleHashBackDiagonal to fill the rectangle using the size for 
the hash pattern.
</dd>
<dt>bsCross</dt>
<dd>
Calls both FillRectangleHashHorizontal and FillRectangleHashVertical to fill 
the rectangle using the size for the hash pattern.
</dd>
<dt>bsDiagCross</dt>
<dd>
Calls booth FillRectangleHashDiagonal and FillRectangleHashBackDiagonal to 
fill the rectangle using the size for the hash pattern.
</dd>
<dt>bsHorizontal</dt>
<dd>
Calls FillRectangleHashHorizontal to fill the rectangle using the size for the 
hash pattern.
</dd>
<dt>bsVertical</dt>
<dd>
Calls FillRectangleHashVertical to fill the rectangle using the size for the 
hash pattern.
</dd>
</dl>
<p>
DoRectangleFill is an overridden method in TLazCanvas. It reimplements the 
method introduced in the TFPPixelCanvas ancestor (in FCL), and does <b>not</b> 
call the inherited method.
</p>
</descr>
<vesion>
Modified in LCL version 3.0 to decrease the bottom and right edges of the 
rectangle by a single pixel. This fixes a difference between the rectangle 
fill and a border drawn in the Rectangle method.
</vesion>
<seealso/>
</element>
<element name="TLazCanvas.DoRectangleFill.Bounds">
<short>Rectangle with the bounds adjusted and used in the method.</short>
</element>

<element name="TLazCanvas.DoPolygonFill">
<short>
Implements a polygon fill algorithm not present in fcl-image prior to FPC 
version 3.2.3.
</short>
<descr>
<p>
Implements a polygon fill algorithm not present in fcl-image. Part of the 
algorithm is explained 
<url href="http://alienryderflex.com/polygon_fill/">here</url>.
</p>
<p>
DoPolygonFill is defined when using FPC versions prior to 3.2.3. In FPC 3.2.3, 
the method already exists in the TFPPixelCanvas ancestor and is not needed in 
TLazCanvas.
</p>
</descr>
<version>
Modified in LCL versions after 2.2.4 to call DrawPixel instead of SetColor 
when drawing pixels between points on the polygon. This allows the DrawingMode 
(opacity, alphablending, custom) to be applied to the pixels. Adds support for 
the non-zero winding rule in the fill operation.
</version>
<seealso>
<link id="TLazCanvas.AlphaBlend"/>
<link id="TLazCanvas.SetColor"/>
</seealso>
</element>
<element name="TLazCanvas.DoPolygonFill.points">
<short>Array with the TPoint records representing the polygon vertices.</short>
</element>

<element name="TLazCanvas.DoLine">
<short>
Draws a line using the specified coordinates and Pen for the canvas.
</short>
<descr/>
<seealso/>
</element>
<element name="TLazCanvas.DoLine.x1">
<short>Initial horizontal coordinate for the line.</short>
</element>
<element name="TLazCanvas.DoLine.y1">
<short>Initial vertical coordinate for the line.</short>
</element>
<element name="TLazCanvas.DoLine.x2">
<short>Terminal horizontal coordinate for the line.</short>
</element>
<element name="TLazCanvas.DoLine.y2">
<short>Terminal vertical coordinate for the line.</short>
</element>

<element name="TLazCanvas.DoCopyRect">
<short>
Performs actions needed to copy a source rectangle from the specified canvas.
</short>
<descr>
<p>
<var>DoCopyRect</var> is an overridden method in <var>TLazCanvas</var>. It is 
used to copy values from the specified source rectangle in the Canvas argument 
to the location specified in X and Y. DoCopyRect reimplements the method from 
an ancestor class (TFPPixelCanvas).
</p>
<p>
<var>X</var> and <var>Y</var> contain the left, top coordinates on the Lazarus 
canvas where the copied values are stored.
</p>
<p>
<var>Canvas</var> is the TFPCustomCanvas instance with the values for the 
SourceRect argument.
</p>
<p>
<var>SourceRect</var> is the TRect instance width the Left, Top, Right and 
Bottom coordinates for the rectangular region copied from Canvas.
</p>
<p>
DoCopyRect calls the CanvasCopyRect method to perform the actions needed to 
perform the copy operation using the specified arguments.
</p>
</descr>
<seealso>
<link id="TLazCanvas.CanvasCopyRect"/>
</seealso>
</element>
<element name="TLazCanvas.DoCopyRect.x">
<short>
Left coordinate where the copied values are stored on the Lazarus canvas.
</short>
</element>
<element name="TLazCanvas.DoCopyRect.y">
<short>
Top coordinate where the copied values are stored on the Lazarus canvas.
</short>
</element>
<element name="TLazCanvas.DoCopyRect.canvas">
<short>
Canvas instance that is the source for the values copied in the method.
</short>
</element>
<element name="TLazCanvas.DoCopyRect.SourceRect">
<short>
TRect instance with the Canvas coordinates copied in the method.
</short>
</element>

<element name="TLazCanvas.DoDraw">
<short>
Performs actions needed to draws the specified image at the given coordinates 
using AlphaBlending.
</short>
<descr>
<p>
<var>DoDraw</var> is an overridden method in <var>TLazCanvas</var>. It 
reimplements the method from an ancestor class (TFPixelCanvas), and calls the 
AlphaBlend_Image method to draw the specified image at the given position.
</p>
<p>
<var>X</var> and <var>Y</var> contain the left and top coordinates on the 
Lazarus canvas where the image is drawn.
</p>
<p>
<var>AImage</var> is the TFPCustomImage instance drawn at the specified 
position.
</p>
<p>
DoDraw is used to implement the DoDrawImage method.
</p>
</descr>
<seealso>
<link id="TLazCanvas.AlphaBlend_Image"/>
</seealso>
</element>
<element name="TLazCanvas.DoDraw.x">
<short>
Left coordinate on the Lazarus canvas where the specified image is drawn.
</short>
</element>
<element name="TLazCanvas.DoDraw.y">
<short>
Top coordinate on the Lazarus canvas where the specified image is drawn.
</short>
</element>
<element name="TLazCanvas.DoDraw.AImage">
<short>
Image drawn on the Lazarus canvas at the specified position.
</short>
</element>

<element name="TLazCanvas.HasNoImage">
<short>Indicates if a valid image was provided in the constructor.</short>
<descr>
<p>
<var>HasNoImage</var> is a <var>Boolean</var> member used to indicate if a 
valid <var>TFPCustomImage</var> was provided as an argument to the 
<var>Create</var> constructor. Used in the implementation of the 
<var>UpdateControlLazImageAndCanvas</var> routine for non-native custom drawn 
window controls.
</p>
</descr>
<seealso>
<link id="TLazCanvas.Create"/>
</seealso>
</element>

<element name="TLazCanvas.NativeDC">
<short>Native device context for the canvas.</short>
<descr>
<p>
<var>NativeDC</var> is a <var>PtrInt</var> member which contains the device 
context used to render a custom-drawn LCL control.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvas.ExtraFontData">
<short>
Member with extra FreeType font data from the canvas or device context.
</short>
<descr>Used in custom-drawn LCL controls.</descr>
<seealso/>
</element>

<element name="TLazCanvas.ImageFormat">
<short>
Member with the TLazCanvasImageFormat instance used to speed up drawing.
</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvas.SelectedBitmap">
<short>Member with the GDI Handle for an image.</short>
<descr>Used in custom-drawn LCL controls.</descr>
<seealso/>
</element>

<element name="TLazCanvas.Create">
<short>Constructor for the class instance.</short>
<descr>
<p>
<var>Create</var> is the constructor for the class instance. Create calls the 
inherited constructor using <var>AnImage</var> as an argument.
</p>
<p>
Create allocates resources for the <var>GraphicStateList</var> property. 
Create sets the value for the <var>HasNoImage</var> member to <b>True</b> 
when <var>AnImage</var> has not been assigned (contains <b>Nil</b>).
</p>
</descr>
<seealso>
<link id="TLazCanvas.HasNoImage"/>
</seealso>
</element>
<element name="TLazCanvas.Create.AnImage">
<short>Screen image for the control rendered on the canvas.</short>
</element>

<element name="TLazCanvas.Destroy">
<short>Destructor for the class instance.</short>
<descr>
<p>
<var>Destroy</var> is the overridden destructor for the class instance. 
Destroy ensures that resources allocated for <var>GraphicStateList</var>, 
<var>AssignedBrush</var>, and <var>AssignedPen</var> are freed. Destroy calls 
the inherited destructor prior to exiting from the method.
</p>
</descr>
<seealso>
<link id="TLazCanvas.AssignedBrush"/>
<link id="TLazCanvas.AssignedPen"/>
</seealso>
</element>

<element name="TLazCanvas.SetLazClipRegion">
<short>Sets the value in the ClipRegion property.</short>
<descr/>
<seealso/>
</element>
<element name="TLazCanvas.SetLazClipRegion.ARegion">
<short>Region stored in the property.</short>
</element>

<element name="TLazCanvas.SaveState">
<short>Saves the current canvas state in the GraphicStateList member.</short>
<descr>
<p>
<var>SaveState</var> is an <var>Integer</var> function used to save the 
current canvas state in the <var>GraphicStateList</var> member. SaveState 
creates an instance of <var>TLazCanvasState</var> with copies of the current 
values for <var>Brush</var>, <var>Pen</var>, and <var>Font</var>. Values from 
<var>BaseWindowOrg</var>, <var>WindowOrg</var>, and <var>Clipping</var> are 
also assigned to the class instance.
</p>
<p>
The return value contains the ordinal position in <var>GraphicStateList</var> 
where the canvas state was added in the method.
</p>
<p>
Use <var>RestoreState</var> to restore the canvas to the state stored at a 
specified position in the list.
</p>
</descr>
<seealso>
<link id="TLazCanvas.AssignedBrush"/>
<link id="TLazCanvas.AssignedPen"/>
<link id="TLazCanvas.AssignedFont"/>
<link id="TLazCanvas.BaseWindowOrg"/>
<link id="TLazCanvas.WindowOrg"/>
<link id="TLazCanvas.RestoreState"/>
</seealso>
</element>
<element name="TLazCanvas.SaveState.Result">
<short>
Ordinal position in GraphicStateList where the saved canvas state was stored.
</short>
</element>

<element name="TLazCanvas.RestoreState">
<short>
Restores the canvas to the state stored at the specified position.
</short>
<descr/>
<seealso/>
</element>
<element name="TLazCanvas.RestoreState.AIndex">
<short>Ordinal position in GraphicStateList restored in the method.</short>
</element>

<element name="TLazCanvas.ResetCanvasState">
<short>
Sets the canvas to the default values/state used in the LCL TCanvas class.
</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvas.AlphaBlend">
<short>
Alpha blends the specified content from the source canvas onto the canvas 
instance.
</short>
<descr>
<p>
<var>AlphaBlend</var> combines the content in <var>ASource</var> with the 
current class instance to create the appearance of an image with partial or 
full transparency. The current class instance provides the background for the 
combined content.
</p>
<p>
<var>ADestX</var> and <var>ADestY</var> provides the left and top coordinates 
where the content from ASource is overlayed.
</p>
<p>
<var>ASourceX</var>, <var>ASourceY</var>, <var>ASourceWidth</var> and <var>
ASourceHeight</var> contain the coordinates and dimensions for the image area 
retrieved from the ASource canvas.
</p>
<p>
AlphaBlend ensures that the specified source content is not too large for the 
destination area. The dimensions in ASourceWidth and ASourceHeight are 
adjusted if any part of the image is outside the destination area.
</p>
<p>
AlphaBlend creates an inverse mask for the alpha channel used on the pixels in 
ASource. The mask is applied to the RGB components for the Colors in the 
current class instance. The alpha channel in Colors is set to alphaOpaque for 
the combined content.
</p>
<p>
AlphaBlend is used in the implementation of the AlphaBlend_Image method.
</p>
<p>
<b>Topics of Interest (but not documented in FCL)</b>
</p>
<ul>
<li>TFPCustomCanvas.Colors (in <file>fpcanvas.pp</file>)</li>
<li>TFPImageCanvas (in <file>fpimgcanv.pp</file>)</li>
<li>TFPColor (in <file>fpimage.pp</file>)</li>
</ul>
</descr>
<seealso>
<link id="TLazCanvas.AlphaBlend_Image"/>
<link id="TLazCanvas.AlphaBlendIgnoringDestPixels"/>
</seealso>
</element>
<element name="TLazCanvas.AlphaBlend.ASource">
<short>
Lazarus canvas with the content alpha blended onto the current class instance.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ADestX">
<short>
Left coordinate where the content in ASource is applied.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ADestY">
<short>
Top coordinate where the content in ASource is applied.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ASourceX">
<short>
Left coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ASourceY">
<short>
Top coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ASourceWidth">
<short>
Width (in pixels) of the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend.ASourceHeight">
<short>
Height (in pixels) of the content in ASource applied in the method.
</short>
</element>

<element name="TLazCanvas.AlphaBlendIgnoringDestPixels">
<short>Performs an AlphaBlend operation assuming a white background.</short>
<descr>
<p>
This is a safer version for use where the destination pixels may not be 
consistent or valid. It will draw as if the target area contained opaque 
white pixels.
</p>
</descr>
<seealso>
<link id="TLazCanvas.AlphaBlend"/>
</seealso>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ASource">
<short>
Lazarus canvas with the content alpha blended onto the current class instance.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ADestX">
<short>
Left coordinate where the content in ASource is applied.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ADestY">
<short>
Top coordinate where the content in ASource is applied.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ASourceX">
<short>
Left coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ASourceY">
<short>
Top coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ASourceWidth">
<short>
Width (in pixels) of the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlendIgnoringDestPixels.ASourceHeight">
<short>
Height (in pixels) of the content in ASource applied in the method.
</short>
</element>

<element name="TLazCanvas.AlphaBlend_Image">
<short>AlphaBlends the specified image onto the canvas.</short>
<descr/>
<seealso>
<link id="TLazCanvas.AlphaBlend"/>
<link id="TLazCanvas.AlphaBlendIgnoringDestPixels"/>
</seealso>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ASource">
<short>
TFPCustomImage instance with the content applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ADestX">
<short>
Left coordinate where the content in ASource is applied to the canvas.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ADestY">
<short>
Top coordinate where the content in ASource is applied to the canvas.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ASourceX">
<short>
Left coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ASourceY">
<short>
Top coordinate for the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ASourceWidth">
<short>
Width (in pixels) of the content in ASource applied in the method.
</short>
</element>
<element name="TLazCanvas.AlphaBlend_Image.ASourceHeight">
<short>
Height (in pixels) of the content in ASource applied in the method.
</short>
</element>

<element name="TLazCanvas.DoDrawImage">
<short>
Calls DoDraw for the specified image and coordinates.
</short>
<descr/>
<seealso>
<link id="TLazCanvas.DoDraw"/>
</seealso>
</element>
<element name="TLazCanvas.DoDrawImage.x">
<short>
Left coordinate where the specified image is drawn on the Lazarus canvas.
</short>
</element>
<element name="TLazCanvas.DoDrawImage.y">
<short>
Top coordinate where the specified image is drawn on the Lazarus canvas.
</short>
</element>
<element name="TLazCanvas.DoDrawImage.AImage">
<short>
TFPCustomImage instance with the content rendered to the canvas.
</short>
</element>

<element name="TLazCanvas.CanvasCopyRect">
<short>
Copies the contents of a supported image format in ASource to the canvas.
</short>
<descr/>
<seealso>
<link id="TLazCanvas.DoCopyRect"/>
</seealso>
</element>

procedure CanvasCopyRect(ASource: TFPCustomCanvas; 
  const ADestX, ADestY, ASourceX, ASourceY, 
  ASourceWidth, ASourceHeight: Integer);

<element name="TLazCanvas.CanvasCopyRect.ASource">
<short>
TFPCustomCanvas instance with the content copied in the method.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ADestX">
<short>
Left coordinate on the canvas where the content in ASource is copied.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ADestY">
<short>
Top coordinate on the canvas where the content in ASource is copied.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ASourceX">
<short>
Left coordinate for the content in ASource copied in the method.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ASourceY">
<short>
Top coordinate for the content in ASource copied in the method.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ASourceWidth">
<short>
Width (in pixels) for the content in ASource copied in the method.
</short>
</element>
<element name="TLazCanvas.CanvasCopyRect.ASourceHeight">
<short>
Height (in pixels) for the content in ASource copied in the method.
</short>
</element>

<element name="TLazCanvas.FillColor">
<short>Fills the entire drawing area with the specified color.</short>
<descr>
<p>
Fills the entire drawing area with the specified color. 
<var>AIgnoreClippingAndWindowOrg</var> speeds up canvas drawing operations, 
but it is dangerous; don't use it unless you know what you are doing.
</p>
</descr>
<seealso/>
</element>
<element name="TLazCanvas.FillColor.AColor">
<short>Color applied to the canvas area.</short>
</element>
<element name="TLazCanvas.FillColor.AIgnoreClippingAndWindowOrg">
<short>
<b>True</b> ignores the canvas clipping region and window origin, and fills 
all pixels for an underlying Image with the specified color. <b>False</b> (the 
default) limits the scope to the Width and Height for the canvas - not the 
range of pixels in the Image.
</short>
</element>

<element name="TLazCanvas.Polygon">
<short>
Overloaded method which adds support for the non-zero winding rule.
</short>
<descr>
<p>
<var>Polygon()</var> overloads an equally-named method inherited from <var>TFPCustomCanvas</var> 
which
fills a polygon via <var>DoPolygonFill()</var>. 
By default, the even-odd rule is applied for filling. 
The current overload, however, adds support for filling the polygon 
by the <url href="https://en.wikipedia.org/wiki/Nonzero-rule/">non-zero winding rule</url>.
</p>
<p>
In each case, the polygon is filled by drawing horizontal lines across the polygon 
starting at the left 
The intersection points of this line with the polygon segments are calculated 
and sorted from left to right. 
</p>
<p>
In the even-odd rule, lines are drawn between adjacent intersection points in 
an alternating way. 
</p>
<p>
In the non-zero winding rule the "winding number"
(starting at zero for each line) is incremented/decremented depending on whether
the hit polygon segment is oriented upward or downward.
The following line segment is drawn only when the accumulated winding number 
is not zero.
</p>
<p>
The non-zero winding rule is selected when the <var>Winding</var> argument of the 
method is <b>true</b>. 
Otherwise the even-odd rule is applied.
</p>
<p>
The <var>DrawPixel()</var> method is called along the filling lines in order to apply the 
brush color to the canvas pixels in an either opaque or semi-transparent way.
</p>
</descr>
<version>
Added in LCL version 3.0.
</version>
<seealso/>
</element>
<element name="TLazCanvas.Polygon.Points">
<short>
Array with the TPoint instances for the vertices on the polygon.
</short>
</element>
<element name="TLazCanvas.Polygon.Winding">
<short>
<b>True</b> if the non-zero winding rule is enabled for the canvas instance.
Otherwise the polygon is filled by means of the "even-odd" rule in which 
alternating horizontal lines are drawn between pairs of polygon intersection 
points.
</short>
</element>

<element name="TLazCanvas.AssignPenData">
<short>Sets the Pen data for the canvas.</short>
<descr>
<p>
Utilized by <var>LCLIntf.SelectObject</var> and by the 
<var>RestoreState</var> method. This is needed because calling 
<var>Assign</var> for the <var>Pen</var>, <var>Brush</var>, or 
<var>Font</var> properties raises exceptions.
</p>
</descr>
<seealso/>
</element>
<element name="TLazCanvas.AssignPenData.APen">
<short>Pen data stored in the method.</short>
</element>

<element name="TLazCanvas.AssignBrushData">
<short>Sets the Brush data for the canvas.</short>
<descr>
<p>
Utilized by <var>LCLIntf.SelectObject</var> and by the 
<var>RestoreState</var> method. This is needed because calling 
<var>Assign</var> for the <var>Pen</var>, <var>Brush</var>, or 
<var>Font</var> properties raises exceptions.
</p>
</descr>
<seealso/>
</element>
<element name="TLazCanvas.AssignBrushData.ABrush">
<short>Brush data stored in the method.</short>
</element>

<element name="TLazCanvas.AssignFontData">
<short>Sets the Font data for the canvas.</short>
<descr>
<p>
AssignFontData copies property values in AFont to the Font for class instance, 
including:
</p>
<ul>
<li>FPColor</li>
<li>Name</li>
<li>Size</li>
<li>Bold</li>
<li>Italic</li>
<li>Underline</li>
<li>Strikethrough</li>
</ul>
<p>
No actions are performed in the method if AFont has not been assigned 
(contains <b>Nil</b>.
</p>
<p>
Utilized by <var>LCLIntf.SelectObject</var> and by the 
<var>RestoreState</var> method. This is needed because calling 
<var>Assign</var> for the <var>Pen</var>, <var>Brush</var>, or 
<var>Font</var> properties raises exceptions.
</p>
</descr>
<seealso/>
</element>
<element name="TLazCanvas.AssignFontData.AFont">
<short>
TFPCustomFont instance with the attributes assigned to the Font for the canvas.
</short>
</element>

<element name="TLazCanvas.AssignedPen">
<short>Pen assigned to the canvas.</short>
<descr>
<p>
These properties are utilized to implement <var>LCLIntf.SelectObject</var> to 
keep track of which pen/brush/font handle was assigned to this canvas. They 
are not utilized by <var>TLazCanvas</var> itself.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvas.AssignedBrush">
<short>Brush assigned to the canvas.</short>
<descr>
<p>
These properties are used to implement <var>LCLIntf.SelectObject</var> to 
keep track of which pen/brush/font handle was assigned to this canvas. They 
are not utilized by <var>TLazCanvas</var> itself.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvas.AssignedFont">
<short>Font assigned to the canvas.</short>
<descr>
<p>
These properties are used to implement <var>LCLIntf.SelectObject</var> to 
keep track of which pen/brush/font handle was assigned to this canvas. They 
are not utilized by <var>TLazCanvas</var> itself.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvas.BaseWindowOrg">
<short>Base window origin for the canvas.</short>
<descr>
<p>
The values in <var>WindowOrg</var> are relative to the coordinates in 
<var>BaseWindowOrg</var>. BaseWindowOrg coordinates are relative to the 
canvas for the containing Form. It is useful when implementing the non-native 
windowed controls.
</p>
</descr>
<seealso/>
</element>

<element name="TLazCanvas.ClipRegion">
<short>Clipping region for the canvas.</short>
<descr/>
<seealso/>
</element>

<element name="TLazCanvas.WindowOrg">
<short>Window origin for the canvas.</short>
<descr>
<p>
Contains the absolute coordinates for the canvas with 
<var>BaseWindowOrg</var> summed up.
</p>
</descr>
<seealso/>
</element>

</module>
<!-- LazCanvas -->
</package>
</fpdoc-descriptions>
