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Docs: LCL/imglist. Updates Scaled and OnGetWidthForPPI topics in TCustomImageList.

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* Restores details about OnGetWidthForPPI removed in the previous commit from the TCustomImageList.Scaled topic.
* Adds a code example in the TCustomImageList.OnGetWidthForPPI topic,

(cherry picked from commit b583b3fa04)
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dsiders 2023-12-22 16:09:27 +00:00
parent c61723c0f1
commit 5cbbd5956a
1 changed files with 21 additions and 6 deletions
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27
docs/xml/lcl/imglist.xml
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@ -6569,8 +6569,13 @@ density (Pixels per Inch). If the scaled image size is one of the Resolutions
found in the image list, the images in the Resolution are used. If an image found in the image list, the images in the Resolution are used. If an image
size is needed that does not exist in Resolutions, the next smaller size is size is needed that does not exist in Resolutions, the next smaller size is
selected from the predefined images by using the WidthForPPI property and a selected from the predefined images by using the WidthForPPI property and a
specified PPI setting. The ResolutionForPPI property provides access to an specified PPI setting.
image list using the scaled image size. </p>
<p>
The <var>OnGetWidthForPPI</var> event handler is signalled (when assigned) to
allow the calculated image width to be overridden. Applications can provide a
<var>TCustomImageListGetWidthForPPI</var> procedure which uses custom scaling
logic, or performs simple image width substitution for a given display density.
</p> </p>
<p> <p>
See <link id="TCustomImageList.WidthForPPI">WidthForPPI</link> for information See <link id="TCustomImageList.WidthForPPI">WidthForPPI</link> for information
@ -6578,6 +6583,10 @@ about use of the pixels per inch setting to derive the scaling factor and the
resulting size for images. resulting size for images.
</p> </p>
<p> <p>
The ResolutionForPPI property provides access to an image list using an image
size scaled to a specific PPI setting.
</p>
<p>
When Scaled is <b>False</b>, images are not dynamically scaled. The Width and When Scaled is <b>False</b>, images are not dynamically scaled. The Width and
Height specified in the image list are used. Height specified in the image list are used.
</p> </p>
@ -6591,10 +6600,6 @@ resolutions used in the image list. At run-time, use the methods provided in
the class instance to maintain the image list. the class instance to maintain the image list.
</p> </p>
<p> <p>
Use the <var>OnGetWidthForPPI</var> event handler to override or substitute the
image size used for a given display density (PPI).
</p>
<p>
Scaled is used in the implementation of the <var>GetResolutionForPPI</var> Scaled is used in the implementation of the <var>GetResolutionForPPI</var>
and <var>GetWidthForPPI</var> methods which implement the ResolutionForPPI and and <var>GetWidthForPPI</var> methods which implement the ResolutionForPPI and
WidthForPPI properties (respectively). WidthForPPI properties (respectively).
@ -6679,6 +6684,16 @@ the event handler which handles image width calculations or substitutions.
The image width is returned in the <var>AResultWidth</var> parameter for the The image width is returned in the <var>AResultWidth</var> parameter for the
event handler. event handler.
</p> </p>
<p>
For example:
</p>
<code>
procedure TForm1.ImageList1GetWidthForPPI(Sender: TCustomImageList;
AImageWidth, APPI: Integer; var AResultWidth: Integer);
begin
AResultWidth := AImageWidth * APPI div 96;
end;
</code>
</descr> </descr>
<seealso> <seealso>
<link id="TCustomImageListGetWidthForPPI"/> <link id="TCustomImageListGetWidthForPPI"/>