Fixed DirectX RTL text issue where it'd be over other text / offscreen

src/renderer/dx/CustomTextLayout.cpp

@@ -498,6 +498,20 @@ CustomTextLayout::CustomTextLayout(IDWriteFactory2* const factory,
  glyphRunDescription.stringLength = run.textLength;
  glyphRunDescription.textPosition = run.textStart;
 
+ // Calculate the origin for the next run based on the amount of space
+ // that would be consumed. We are doing this calculation now, not after,
+ // because if the text is RTL then we need to advance immediately, before the
+ // write call since DirectX expects the origin to the RIGHT of the text for RTL.
+ const auto postOriginX = std::accumulate(_glyphAdvances.begin() + run.glyphStart,
+ _glyphAdvances.begin() + run.glyphStart + run.glyphCount,
+ mutableOrigin.x);
+
+ // Check for RTL, if it is, apply space adjustment.
+ if (WI_IsFlagSet(glyphRun.bidiLevel, 1))
+ {
+ mutableOrigin.x = postOriginX;
+ }
+
  // Try to draw it
  RETURN_IF_FAILED(renderer->DrawGlyphRun(clientDrawingContext,
  mutableOrigin.x,
@@ -507,10 +521,9 @@ CustomTextLayout::CustomTextLayout(IDWriteFactory2* const factory,
  &glyphRunDescription,
  nullptr));
 
- // Shift origin to the right for the next run based on the amount of space consumed.
- mutableOrigin.x = std::accumulate(_glyphAdvances.begin() + run.glyphStart,
- _glyphAdvances.begin() + run.glyphStart + run.glyphCount,
- mutableOrigin.x);
+ // Either way, we should be at this point by the end of writing this sequence,
+ // whether it was LTR or RTL.
+ mutableOrigin.x = postOriginX;
  }
  }
  CATCH_RETURN();