Render Using Direct2D

Direct2D provides methods for rendering either text with formatting described by only an IDWriteTextFormat or an IDWriteTextLayout to a Direct2D surface.

Rendering Text Described by IDWriteTextFormat

To render a string using an IDWriteTextFormat object to describe the formatting for the entire string, use the ID2D1RenderTarget::DrawText method provided by Direct2D.

1. Define the area for the text layout by retrieving the dimensions of the rendering area, and create a Direct2D rectangle that has the same dimensions.

   D2D1_RECT_F layoutRect = D2D1::RectF(
       static_cast<FLOAT>(rc.left) / dpiScaleX_,
       static_cast<FLOAT>(rc.top) / dpiScaleY_,
       static_cast<FLOAT>(rc.right - rc.left) / dpiScaleX_,
       static_cast<FLOAT>(rc.bottom - rc.top) / dpiScaleY_
       );
   
   

2. Use the ID2D1RenderTarget::DrawText method and the IDWriteTextFormat object to render text to the screen. The ID2D1RenderTarget::DrawText method takes the following parameters:

   • A string to render.
   • A pointer to an IDWriteTextFormat interface.
   • A Direct2D layout rectangle.
   • A pointer to an interface that exposes ID2D1Brush.

   pRT_->DrawText(
       wszText_,        // The string to render.
       cTextLength_,    // The string's length.
       pTextFormat_,    // The text format.
       layoutRect,       // The region of the window where the text will be rendered.
       pBlackBrush_     // The brush used to draw the text.
       );
   
   

Rendering a IDWriteText Layout Object

To draw the text with the text layout settings specified by the IDWriteTextLayout object, change the code in the MultiformattedText::DrawText method to use IDWriteTextLayout::DrawTextLayout.

1. Delcare a D2D1_POINT_2F variable and set it to the upper-left point of the window.

   D2D1_POINT_2F origin = D2D1::Point2F(
       static_cast<FLOAT>(rc.left / dpiScaleX_),
       static_cast<FLOAT>(rc.top / dpiScaleY_)
       );
   
   

2. Draw the text to the screen by calling the ID2D1RenderTarget::DrawTextLayout method of the Direct2D render target and passing the IDWriteTextLayout pointer.

   pRT_->DrawTextLayout(
       origin,
       pTextLayout_,
       pBlackBrush_
       );