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LibWeb: Implement CanvasRenderingContext2D.measureText

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This requires an implementation of the "text preparation algorithm" as
specified here:

html.spec.whatwg.org/multipage/canvas.html#text-preparation-algorithm

However, we're missing a lot of things such as the
CanvasTextDrawingStyles interface, so most of the algorithm was not
implemented. Additionally, we also are not able to use a LineBox like
the algorithm suggests, because our layouting infra is not up to the
task yet. The prepare_text function does nothing other than figuring out
the width of the given text and return glyphs with offsets at the
moment.
This commit is contained in:
sin-ack 2021-12-30 22:15:38 +00:00 • committed by Linus Groh
parent 732e41714a
commit 9121cc7cae
10 changed files with 253 additions and 0 deletions
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17
Userland/Libraries/LibWeb/HTML/TextMetrics.idl Normal file
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interface TextMetrics {
// x-direction
readonly attribute double width; // advance width
readonly attribute double actualBoundingBoxLeft;
readonly attribute double actualBoundingBoxRight;
// y-direction
readonly attribute double fontBoundingBoxAscent;
readonly attribute double fontBoundingBoxDescent;
readonly attribute double actualBoundingBoxAscent;
readonly attribute double actualBoundingBoxDescent;
readonly attribute double emHeightAscent;
readonly attribute double emHeightDescent;
readonly attribute double hangingBaseline;
readonly attribute double alphabeticBaseline;
readonly attribute double ideographicBaseline;
};