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Sign upFixed calculation of glyph dimensions on Windows #82
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The dimensions in the `DWRITE_GLYPH_METRICS` are a bit special: the `rightSideBearing` is measured from the right edge of the character boundary, not the left edge. So, doing (right - left) would usually return a negative or very small number, which, when casted to a u32 in an unsafe block, would silently overflow to a very large number and make webrender crash. Therefore, in order to calculate the metrics correctly, we have to first calculate the full width of the character, then subtract the right and left edges, same width the height.
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Merged, thanks! |
bors-servo
referenced
this pull request
in servo/webrender
May 8, 2018
…=kvark Final compile fixes for pathfinder Closes #2645. Note: On Windows, pathfinder won't yet run properly, partly due to https://github.com/pcwalton/pathfinder/pull/82 and partly due to some `RenderTask`-related bugs (currently it crashes with "unexpected render task: glyph task") in ` webrender::render_task::RenderTask::uv_rect_kind`. However, pathfinder now at least compiles on Windows, Linux and Mac. Also added various `#[derive(Debug)]` necessary for debugging the pathfinder crashes. <!-- Reviewable:start --> --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/webrender/2723) <!-- Reviewable:end -->
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fschutt commentedMay 3, 2018
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edited
The dimensions in the
DWRITE_GLYPH_METRICSare a bit special: therightSideBearingis measured from the right edge of the character boundary, not the left edge.So, doing (right - left) would usually return a negative or very small number, which, when casted to a u32 in an unsafe block, would silently overflow to a very large number and make webrender crash.
Therefore, in order to calculate the metrics correctly, we have to first calculate the full width of the character, then subtract the right and left edges, same width the height.