Start scaffolding web_canvas backend

example/index.html

@@ -13,21 +13,24 @@
 				}
 			};
 
-			fetch('ghostty-term.wasm').then(response =>
+			fetch('ghostty-wasm.wasm').then(response =>
 				response.arrayBuffer()
 			).then(bytes =>
 				WebAssembly.instantiate(bytes, importObject)
 			).then(results => {
 				const {
-					terminal_new,
-					terminal_free,
-					terminal_print,
+					atlas_new,
+					atlas_free,
+					atlas_reserve,
+					free,
+					memory,
 				} = results.instance.exports;
 
-				const term = terminal_new(80, 80);
-				console.log(term);
-				terminal_free(term);
-				terminal_print('a');
+				const atlas = atlas_new(512, 0);
+				const reg = atlas_reserve(atlas, 10, 10);
+				console.log(reg);
+				free(reg);
+				atlas_free(atlas);
 			});
 		</script>
 	</body>

src/font/Atlas.zig

@@ -49,10 +49,10 @@ modified: bool = false,
 /// updated in-place.
 resized: bool = false,
 
-pub const Format = enum {
-    greyscale,
-    rgb,
-    rgba,
+pub const Format = enum(u8) {
+    greyscale = 0,
+    rgb = 1,
+    rgba = 2,
 
     pub fn depth(self: Format) u8 {
         return switch (self) {
@@ -310,33 +310,33 @@ pub const Wasm = struct {
     const wasm = @import("../wasm.zig");
     const alloc = wasm.alloc;
 
-    const FormatInt = @typeInfo(Format).Enum.tag_type;
-    export const ATLAS_FORMAT_GREYSCALE: u8 = @enumToInt(Format.greyscale);
-    export const ATLAS_FORMAT_RGB: u8 = @enumToInt(Format.rgb);
-    export const ATLAS_FORMAT_RGBA: u8 = @enumToInt(Format.rgba);
-
     export fn atlas_new(size: u32, format: u8) ?*Atlas {
         const atlas = init(
             alloc,
             size,
-            @intToEnum(Format, @intCast(FormatInt, format)),
+            @intToEnum(Format, format),
         ) catch return null;
         const result = alloc.create(Atlas) catch return null;
         result.* = atlas;
         return result;
     }
 
-    export fn atlas_reserve(self: *Atlas, width: u32, height: u32) Region {
-        return self.reserve(alloc, width, height) catch .{
-            .x = 0,
-            .y = 0,
-            .width = 0,
-            .height = 0,
-        };
+    /// The return value for this should be freed by the caller with "free".
+    export fn atlas_reserve(self: *Atlas, width: u32, height: u32) ?*Region {
+        return atlas_reserve_(self, width, height) catch return null;
     }
 
-    export fn atlas_set(self: *Atlas, reg: Region, data: [*]const u8, len: usize) void {
-        self.set(reg, data[0..len]);
+    fn atlas_reserve_(self: *Atlas, width: u32, height: u32) !*Region {
+        const reg = try self.reserve(alloc, width, height);
+        const result = try alloc.create(Region);
+        errdefer alloc.destroy(result);
+        _ = try wasm.toHostOwned(result);
+        result.* = reg;
+        return result;
+    }
+
+    export fn atlas_set(self: *Atlas, reg: *Region, data: [*]const u8, len: usize) void {
+        self.set(reg.*, data[0..len]);
     }
 
     export fn atlas_grow(self: *Atlas, size_new: u32) bool {
@@ -354,6 +354,22 @@ pub const Wasm = struct {
             alloc.destroy(v);
         }
     }
+
+    test "happy path" {
+        var atlas = atlas_new(512, @enumToInt(Format.greyscale)).?;
+        defer atlas_free(atlas);
+
+        const reg = atlas_reserve(atlas, 2, 2).?;
+        defer alloc.destroy(reg);
+        try testing.expect(wasm.isHostOwned(reg));
+        defer wasm.toModuleOwned(reg);
+        try testing.expect(reg.width > 0);
+
+        const data = &[_]u8{ 1, 2, 3, 4 };
+        try testing.expect(!atlas.modified);
+        atlas_set(atlas, reg, data, data.len);
+        try testing.expect(atlas.modified);
+    }
 };
 
 test "exact fit" {

src/font/DeferredFace.zig

@@ -68,6 +68,8 @@ pub fn deinit(self: *DeferredFace) void {
         .fontconfig_freetype => if (self.fc) |*fc| fc.deinit(),
         .coretext => if (self.ct) |*ct| ct.deinit(),
         .freetype => {},
+        // TODO
+        .web_canvas => unreachable,
     }
     self.* = undefined;
 }
@@ -90,6 +92,9 @@ pub fn name(self: DeferredFace) ![:0]const u8 {
         },
 
         .freetype => {},
+
+        // TODO
+        .web_canvas => unreachable,
     }
 
     return "TODO: built-in font names";
@@ -122,6 +127,9 @@ pub fn load(
             return;
         },
 
+        // TODO
+        .web_canvas => unreachable,
+
         // Unreachable because we must be already loaded or have the
         // proper configuration for one of the other deferred mechanisms.
         .freetype => unreachable,
@@ -245,6 +253,9 @@ pub fn hasCodepoint(self: DeferredFace, cp: u32, p: ?Presentation) bool {
             }
         },
 
+        // TODO
+        .web_canvas => unreachable,
+
         .freetype => {},
     }
 

src/font/face.zig

@@ -2,12 +2,14 @@ const builtin = @import("builtin");
 const options = @import("main.zig").options;
 const freetype = @import("face/freetype.zig");
 const coretext = @import("face/coretext.zig");
+const web_canvas = @import("face/web_canvas.zig");
 
 /// Face implementation for the compile options.
 pub const Face = switch (options.backend) {
     .fontconfig_freetype => freetype.Face,
     .coretext => freetype.Face,
     //.coretext => coretext.Face,
+    .web_canvas => web_canvas.Face,
     else => unreachable,
 };
 

src/font/face/web_canvas.zig

@@ -0,0 +1,22 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const freetype = @import("freetype");
+const assert = std.debug.assert;
+const testing = std.testing;
+const Allocator = std.mem.Allocator;
+const font = @import("../main.zig");
+const Glyph = font.Glyph;
+const Library = font.Library;
+const Presentation = font.Presentation;
+const convert = @import("freetype_convert.zig");
+
+const log = std.log.scoped(.font_face);
+
+pub const Face = struct {
+    /// The presentation for this font. This is a heuristic since fonts don't have
+    /// a way to declare this. We just assume a font with color is an emoji font.
+    presentation: Presentation,
+
+    /// Metrics for this font face. These are useful for renderers.
+    metrics: font.face.Metrics,
+};

src/font/main.zig

@@ -25,12 +25,7 @@ pub usingnamespace if (builtin.target.isWasm()) struct {
 pub const options: struct {
     backend: Backend,
 } = .{
-    .backend = if (build_options.coretext)
-        .coretext
-    else if (build_options.fontconfig)
-        .fontconfig_freetype
-    else
-        .freetype,
+    .backend = Backend.default(),
 };
 
 pub const Backend = enum {
@@ -43,14 +38,37 @@ pub const Backend = enum {
     /// CoreText for both font discovery and rendering (macOS).
     coretext,
 
+    /// Use the browser font system and the Canvas API (wasm). This limits
+    /// the available fonts to browser fonts (anything Canvas natively
+    /// supports).
+    web_canvas,
+
+    /// Returns the default backend for a build environment. This is
+    /// meant to be called at comptime.
+    pub fn default() Backend {
+        // Wasm only supports browser at the moment.
+        if (builtin.target.isWasm()) return .web_canvas;
+
+        return if (build_options.coretext)
+            .coretext
+        else if (build_options.fontconfig)
+            .fontconfig_freetype
+        else
+            .freetype;
+    }
+
     /// Helper that just returns true if we should be using freetype. This
     /// is used for tests.
     pub fn freetype(self: Backend) bool {
         return switch (self) {
             .freetype, .fontconfig_freetype => true,
-            .coretext => false,
+            .coretext, .web_canvas => false,
         };
     }
+
+    test "default can run at comptime" {
+        _ = comptime default();
+    }
 };
 
 /// The styles that a family can take.
@@ -71,5 +89,11 @@ pub const Presentation = enum(u1) {
 pub const sprite_index = Group.FontIndex.initSpecial(.sprite);
 
 test {
+    // For non-wasm we want to test everything we can
+    if (!comptime builtin.target.isWasm()) {
         @import("std").testing.refAllDecls(@This());
+        return;
+    }
+
+    _ = Atlas;
 }

src/main_wasm.zig

@@ -1,4 +1,8 @@
 // This is the main file for the WASM module. The WASM module has to
 // export a C ABI compatible API.
 
+pub usingnamespace @import("wasm.zig");
 pub usingnamespace @import("font/main.zig");
+
+// TODO: temporary while we dev this
+pub usingnamespace @import("font/face/web_canvas.zig");