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Improve canvas context caching

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Improve https://github.com/lightpanda-io/browser/pull/2022 to also cache webgl
context and add tests.
This commit is contained in:
Karl Seguin
2026-03-30 12:14:32 +08:00
parent b4e3f246ca
commit 25889ff918
3 changed files with 40 additions and 24 deletions
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10
src/browser/tests/canvas/canvas_rendering_context_2d.html
View File

@@ -148,3 +148,13 @@
}
</script>
<script id=identity>
{
const element = document.createElement('canvas');
const ctx = element.getContext('2d');
testing.expectTrue(ctx === element.getContext('2d'));
testing.expectEqual(null, element.getContext('webgl'));
}
</script>

10
src/browser/tests/canvas/webgl_rendering_context.html
View File

@@ -85,3 +85,13 @@
loseContext.restoreContext();
}
</script>
<script id=identity>
{
const element = document.createElement('canvas');
const ctx = element.getContext('webgl');
testing.expectTrue(ctx === element.getContext('webgl'));
testing.expectEqual(null, element.getContext('2d'));
}
</script>

34
src/browser/webapi/element/html/Canvas.zig
View File

@@ -29,11 +29,7 @@ const OffscreenCanvas = @import("../../canvas/OffscreenCanvas.zig");
const Canvas = @This();
_proto: *HtmlElement,
/// Cached context type. Once set, requesting a different type returns null (per spec).
_context_type: ContextType = .none,
/// Cached 2D rendering context (same object returned on repeated getContext("2d") calls).
_ctx_2d: ?*CanvasRenderingContext2D = null,
_cached: ?DrawingContext = null,
const ContextType = enum { none, @"2d", webgl };
@@ -75,28 +71,28 @@ const DrawingContext = union(enum) {
};
pub fn getContext(self: *Canvas, context_type: []const u8, page: *Page) !?DrawingContext {
if (std.mem.eql(u8, context_type, "2d")) {
// Return cached context if available.
if (self._ctx_2d) |cached| return .{ .@"2d" = cached };
// Per spec: return null if a different context type was already requested.
if (self._context_type != .none) return null;
if (self._cached) |cached| {
const matches = switch (cached) {
.@"2d" => std.mem.eql(u8, context_type, "2d"),
.webgl => std.mem.eql(u8, context_type, "webgl") or std.mem.eql(u8, context_type, "experimental-webgl"),
};
return if (matches) cached else null;
}
const drawing_context: DrawingContext = blk: {
if (std.mem.eql(u8, context_type, "2d")) {
const ctx = try page._factory.create(CanvasRenderingContext2D{ ._canvas = self });
self._ctx_2d = ctx;
self._context_type = .@"2d";
return .{ .@"2d" = ctx };
break :blk .{ .@"2d" = ctx };
}
if (std.mem.eql(u8, context_type, "webgl") or std.mem.eql(u8, context_type, "experimental-webgl")) {
// Per spec: return null if a different context type was already requested.
if (self._context_type != .none and self._context_type != .webgl) return null;
const ctx = try page._factory.create(WebGLRenderingContext{});
self._context_type = .webgl;
return .{ .webgl = ctx };
break :blk .{ .webgl = ctx };
}
return null;
};
self._cached = drawing_context;
return drawing_context;
}
/// Transfers control of the canvas to an OffscreenCanvas.