initial effort for WebGLRenderingContext

src/browser/canvas/WebGLRenderingContext.zig

@@ -0,0 +1,125 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const WebGLRenderingContext = @This();
+_: u8 = 0,
+
+/// On Chrome and Safari, a call to `getSupportedExtensions` returns total of 39.
+/// The reference for it lists lesser number of extensions:
+/// https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Using_Extensions#extension_list
+pub const Extension = union(enum) {
+    ANGLE_instanced_arrays: void,
+    EXT_blend_minmax: void,
+    EXT_clip_control: void,
+    EXT_color_buffer_half_float: void,
+    EXT_depth_clamp: void,
+    EXT_disjoint_timer_query: void,
+    EXT_float_blend: void,
+    EXT_frag_depth: void,
+    EXT_polygon_offset_clamp: void,
+    EXT_shader_texture_lod: void,
+    EXT_texture_compression_bptc: void,
+    EXT_texture_compression_rgtc: void,
+    EXT_texture_filter_anisotropic: void,
+    EXT_texture_mirror_clamp_to_edge: void,
+    EXT_sRGB: void,
+    KHR_parallel_shader_compile: void,
+    OES_element_index_uint: void,
+    OES_fbo_render_mipmap: void,
+    OES_standard_derivatives: void,
+    OES_texture_float: void,
+    OES_texture_float_linear: void,
+    OES_texture_half_float: void,
+    OES_texture_half_float_linear: void,
+    OES_vertex_array_object: void,
+    WEBGL_blend_func_extended: void,
+    WEBGL_color_buffer_float: void,
+    WEBGL_compressed_texture_astc: void,
+    WEBGL_compressed_texture_etc: void,
+    WEBGL_compressed_texture_etc1: void,
+    WEBGL_compressed_texture_pvrtc: void,
+    WEBGL_compressed_texture_s3tc: void,
+    WEBGL_compressed_texture_s3tc_srgb: void,
+    WEBGL_debug_renderer_info: Type.WEBGL_debug_renderer_info,
+    WEBGL_debug_shaders: void,
+    WEBGL_depth_texture: void,
+    WEBGL_draw_buffers: void,
+    WEBGL_lose_context: void,
+    WEBGL_multi_draw: void,
+    WEBGL_polygon_mode: void,
+
+    /// Reified enum type from the fields of this union.
+    const Kind = blk: {
+        const info = @typeInfo(Extension).@"union";
+        const fields = info.fields;
+        var items: [fields.len]std.builtin.Type.EnumField = undefined;
+        for (fields, 0..) |field, i| {
+            items[i] = .{ .name = field.name, .value = i };
+        }
+
+        break :blk @Type(.{
+            .@"enum" = .{
+                .tag_type = std.math.IntFittingRange(0, if (fields.len == 0) 0 else fields.len - 1),
+                .fields = &items,
+                .decls = &.{},
+                .is_exhaustive = true,
+            },
+        });
+    };
+
+    /// Returns the `Extension.Kind` by its name.
+    fn find(name: []const u8) ?Kind {
+        // Just to make you really sad, this function has to be case-insensitive.
+        // So here we copy what's being done in `std.meta.stringToEnum` but replace
+        // the comparison function.
+        const kvs = comptime build_kvs: {
+            const T = Extension.Kind;
+            const EnumKV = struct { []const u8, T };
+            var kvs_array: [@typeInfo(T).@"enum".fields.len]EnumKV = undefined;
+            for (@typeInfo(T).@"enum".fields, 0..) |enumField, i| {
+                kvs_array[i] = .{ enumField.name, @field(T, enumField.name) };
+            }
+            break :build_kvs kvs_array[0..];
+        };
+        const Map = std.StaticStringMapWithEql(Extension.Kind, std.static_string_map.eqlAsciiIgnoreCase);
+        const map = Map.initComptime(kvs);
+        return map.get(name);
+    }
+
+    /// Extension types.
+    pub const Type = struct {
+        pub const WEBGL_debug_renderer_info = packed struct(u64) {
+            UNMASKED_RENDERER_WEBGL: u32 = 0,
+            UNMASKED_VENDOR_WEBGL: u32 = 0,
+        };
+    };
+};
+
+/// Enables a WebGL extension.
+pub fn _getExtension(self: *const WebGLRenderingContext, name: []const u8) ?Extension {
+    _ = self;
+
+    const tag = Extension.find(name) orelse return null;
+
+    return switch (tag) {
+        .WEBGL_debug_renderer_info => @unionInit(Extension, "WEBGL_debug_renderer_info", .{}),
+        inline else => |comptime_enum| @unionInit(Extension, @tagName(comptime_enum), {}),
+    };
+}

src/browser/canvas/root.zig

@@ -1,6 +1,11 @@
 //! Canvas API.
 //! https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API
 
+const WebGLRenderingContext = @import("WebGLRenderingContext.zig");
+const ExtensionType = WebGLRenderingContext.Extension.Type;
+
 pub const Interfaces = .{
-    @import("./CanvasRenderingContext2D.zig"),
+    @import("CanvasRenderingContext2D.zig"),
+    WebGLRenderingContext,
+    ExtensionType.WEBGL_debug_renderer_info,
 };

src/browser/html/elements.zig

@@ -33,6 +33,7 @@ const DataSet = @import("DataSet.zig");
 const StyleSheet = @import("../cssom/StyleSheet.zig");
 const CSSStyleDeclaration = @import("../cssom/CSSStyleDeclaration.zig");
 const CanvasRenderingContext2D = @import("../canvas/CanvasRenderingContext2D.zig");
+const WebGLRenderingContext = @import("../canvas/WebGLRenderingContext.zig");
 
 const WalkerChildren = @import("../dom/walker.zig").WalkerChildren;
 
@@ -497,15 +498,21 @@ pub const HTMLCanvasElement = struct {
         color_space: []const u8 = "srgb",
     };
 
+    /// Returns a drawing context on the canvas, or null if the context identifier
+    /// is not supported, or the canvas has already been set to a different context mode.
     pub fn _getContext(
         ctx_type: []const u8,
         _: ?ContextAttributes,
-    ) !CanvasRenderingContext2D {
-        if (!std.mem.eql(u8, ctx_type, "2d")) {
-            return error.NotSupported;
+    ) ?union(enum) { @"2d": CanvasRenderingContext2D, webgl: WebGLRenderingContext } {
+        if (std.mem.eql(u8, ctx_type, "2d")) {
+            return .{ .@"2d" = .{} };
         }
 
-        return .{};
+        if (std.mem.eql(u8, ctx_type, "webgl") or std.mem.eql(u8, ctx_type, "experimental-webgl")) {
+            return .{ .webgl = .{} };
+        }
+
+        return null;
     }
 };