Category Archives: DirectWrite

MFC Support for DirectWrite – Part 11: About Trimming Again

In a previous article, I showed how to trim a text which overflows the layout box. In the example presented there, the ellipsis is added at the end of truncated text. But if, let’s say, we have to show a long path and file name, it is not meaningful if the file name is not displayed. No problem, this can be easily resolved if have a look at DWRITE_TRIMMING structure which passed to IDWriteTextFormat::SetTrimming. The second parameter is a character code used as delimiter and the third one is the delimiter count. The text is preserved from the end until is found the delimiter which coresponds to delimiter count. For example, if the delimiter is backslash and the delimiter count is 2, a text like “e:\Articles\MFC Support for DirectWrite\DirectWrite Trimming Demo\D2DStaticCtrl.cpp” may be displayed as follows “e:\Articles…\DirectWrite Trimming Demo\D2DStaticCtrl.cpp”.

An example of trimming by using a delimiter

Demo project

Download: DirectWrite Trimming Demo.zip (226)
The demo project is a simple MFC application which demonstrate how to trim text rendered with DirectWrite. You can choose the granularity, the delimiter and the delimiter count and see what is displayed.

DirectWrite Trimming Demo

DirectWrite Trimming Demo

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MFC Support for DirectWrite – Part 10: Outlined Text

In a previous article, I showed the basics of custom text rendering with DirectWrite (see MFC Support for DirectWrite – Part 7: A Step to Custom Rendering). So far so good but it just mimics the default text rendering. Let’s now modify the overridden IDWriteTextRenderer::DrawGlyphRun in order to draw outlined text.

Overridden IDWriteTextRenderer::DrawGlyphRun implementation

A method for drawing outlined text

Basically, the steps where the following:

  1. if pClientDrawingContext parameter is null then perform the default drawing;
  2. otherwhise, call _DrawOutlinedGlyphRun pasing an object that contains the brushes for text outline and fill (COutlinedTextEffect);
  3. create a path geometry (CD2DPathGeometry);
  4. instantiate a geometry sink that is used to populate the path geometry (CD2DGeometrySink);
  5. get IDWriteFontFace interface from DWRITE_GLYPH_RUN structure;
  6. call IDWriteFontFace::GetGlyphRunOutline, passing a bunch of parameters, most of them contained in DWRITE_GLYPH_RUN structure plus our geometry sink;
  7. close the geometry sink;
  8. translate the render target according to the glyph run baseline origin (baselineOriginX and baselineOriginY parameters of DrawGlyphRun);
  9. finally, call CRenderTarget::DrawGeometry and CRenderTarget::FillGeometry and…
  10. …do not forget to restore the initial render target transform.

You can find more details in the demo application attached here. Also you can have a look in the related articles mentioned at the bottom of this page.

Demo project

The demo project draws outlined text in order to make it readable over any background image.
DownloadOutlined Text Demo.zip (365)

Outlined Text demo project

Outlined Text demo project

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MFC Support for DirectWrite – Part 9: Hit-Test

DirectWrite has hit-testing support that can be useful for showing a caret, making a selection, doing some action if the user chicks in a given text range, and so on. The hit-test methods of IDWriteTextLayout interface are HitTestPoint, HitTestTextPosition and HitTestTextRange. Let me show a simple example for each one.

Hit-testing a point

This example calls IDWriteTextLayout::HitTestPoint in the WM_LBUTTONDOWN message handler and keeps in mind the text position in which the user has clicked.

Hit-testing a text position

Further, use the previousy kept in mind text position and call IDWriteTextLayout::HitTestTextPosition when need to draw the caret.

Hit-testing a text range

And finally, here is an example of using IDWriteTextLayout::HitTestTextRange

It can be used, for example, to set the hand cursor when the mouse is moved over the given text range:

or can show some internet page when te user clicks on a “hyperlink”.

More details can be found in the demo examples attached to this article.

Demo projects

I’ve added the hit-test features to DirectWrite Static Control.
Download: Download: MFC Support for DirectWrite Demo (Part 9).zip (351)

MFC DirectWrite - Hit-Test Demo

MFC DirectWrite – Hit-Test Demo

Also here can be found a simpler application, only showing the DirectWrite hit-test features, to be easier understand: Simple DirectWrite Hit-Test Demo.zip (383)

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MFC Support for DirectWrite – Part 8: Trimming

When using “classic” GDI functions i.e. CDC::DrawText, it’s no sweat to trim with ellipsis a single-line text when that text does not fit in the drawing rectangle width, by specifying DT_WORDBREAK flag. We cannot find a similar flag for CRenderTarget::DrawText or CRenderTarget::DrawTextLayout. However, trimming a text is also possible with DirectDraw. All we have to do is the following:

  1. call IDWriteFactory::CreateEllipsisTrimmingSign to create an inline object for trimming, using ellipsis as the omission sign;
  2. pass the created inline object to IDWriteTextFormat::SetTrimming.

Here is a simple code example in an MFC-based application:

Direct2D text trimming code sample

Demo project

Download: MFC Support for DirectWrite Demo (Part 8).zip (331)

The demo project contains sample code for all my DirectWrite-related articles. To demonstrate this one, in Trimming granularity combo, select “Character” or “Word”. Also select “No wrap” in Word wrapping combo then have fun.

MFC DirectWrite Demo Project

MFC DirectWrite Demo Project

 

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Codexpert – 2016 Articles Summary

C++ Programming Language

Microsoft Libraries

Visual C++

See also

Getting Direct2D, DirectWrite and WIC Factories in MFC

MFC library offers a series of wrapper classes over Direct2D and DirectWrite interfaces (see CRenderTarget and CD2D classes). That’s pretty cool because allows to easily load and render images and draw texts, without care too much of direct dealing with COM interfaces.
However, let’s say we have to implemented something different so we need to start creating Direct2D or DirectWrite factories. Of course, we can call D2D1CreateFactory or DWriteCreateFactory functions, but a little bit handier is to use the factories instances created and kept by the MFC framework.

Getting Direct2D, DirectWrite and WIC factories in Visual Studio 2010

In MFC framework shipped with Visual Studio 2010, the instances of ID2D1Factory and IDWriteFactory are created and kept in a global AFX_GLOBAL_DATA structure named afxGlobalData. So, we have to do something like this:

Getting Direct2D, DirectWrite and WIC factories in Visual Studio 2012 – 2015

In Visual Studio 2012, these factory instances have been moved in a D2D-specific structure of type _AFX_D2D_STATE that can be accessed by calling AfxGetD2DState.

Now, we can note that MFC framework keeps also an instance of IWICImagingFactory which is internally used by CD2D classes. That’s also pretty cool; we’ll use it in the following example.

An example of getting and using IWICImagingFactory

Here is a brief example of getting IWICImagingFactory to further read metadata stored in JPEG, TIFF and other image formats.

References and related articles

MFC Support for DirectWrite – Part 7: A Step to Custom Rendering

The previous articles from this series show how to format the text layout using built-in DirectWrite methods. However, as said earlier, we can do more custom formatting (e.g. draw double/triple underline/strikethrough, highlight text and so on). How can be done? First, let’s note that ID2D1RenderTarget::DrawTextLayout internally calls IDWriteTextLayout::Draw which has the following prototype:

We can write our own implementation of IDWriteTextRenderer interface providing custom text rendering then directly call IDWriteTextLayout::Draw instead of CRenderTarget::DrawTextLayout.

Code samples

Demo project

So far, it contains an implementation of IDWriteTextRenderer which does the same as the default one. In a further article I will update it in order to perform custom rendering.
Download: MFC Support for DirectWrite Demo (Part 7).zip (715)

Notes

  • You can find an excellent related article on Petzold Book Blog; see the link below.

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