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gfx: font: add glyph rendering functionality

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Helps hexops/mach#877

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
This commit is contained in:
Stephen Gutekanst 2023-10-03 19:56:20 -07:00
parent 87c3de78f5
commit dfbf3e3603
3 changed files with 88 additions and 13 deletions
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60
src/gfx/font/native/Font.zig
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@ -3,6 +3,9 @@ const ft = @import("mach-freetype");
const harfbuzz = @import("mach-harfbuzz");
const TextRun = @import("TextRun.zig");
const px_per_pt = @import("../main.zig").px_per_pt;
const RenderedGlyph = @import("../main.zig").RenderedGlyph;
const RenderOptions = @import("../main.zig").RenderOptions;
const RGBA32 = @import("../main.zig").RGBA32;
const Font = @This();
@ -11,6 +14,7 @@ var freetype_ready: bool = false;
var freetype: ft.Library = undefined;
face: ft.Face,
bitmap: std.ArrayListUnmanaged(RGBA32) = .{},
pub fn initFreetype() !void {
freetype_ready_mu.lock();
@ -40,8 +44,9 @@ pub fn shape(f: *const Font, r: *TextRun) anyerror!void {
const hb_font = harfbuzz.Font.init(hb_face);
defer hb_font.deinit();
const font_size_pt = @as(f32, @floatFromInt(r.font_size_px)) / px_per_pt;
hb_font.setScale(@as(i32, @intFromFloat(font_size_pt)) * 256, @as(i32, @intFromFloat(font_size_pt)) * 256);
const font_size_pt = r.font_size_px / px_per_pt;
const font_size_pt_frac: i32 = @intFromFloat(font_size_pt * 256.0);
hb_font.setScale(font_size_pt_frac, font_size_pt_frac);
hb_font.setPTEM(font_size_pt);
// TODO: optionally pass shaping features?
@ -52,6 +57,53 @@ pub fn shape(f: *const Font, r: *TextRun) anyerror!void {
r.positions = r.buffer.getGlyphPositions() orelse return error.OutOfMemory;
}
pub fn deinit(f: *const Font) void {
f.face.deinit();
pub fn render(f: *Font, allocator: std.mem.Allocator, glyph_index: u32, opt: RenderOptions) anyerror!RenderedGlyph {
// TODO: DPI configuration
const dpi = 72;
const font_size_pt = opt.font_size_px / px_per_pt;
const font_size_pt_frac: i32 = @intFromFloat(font_size_pt * 64.0);
f.face.setCharSize(font_size_pt_frac, font_size_pt_frac, dpi, dpi) catch return error.RenderError;
f.face.loadGlyph(glyph_index, .{ .render = true }) catch return error.RenderError;
const glyph = f.face.glyph();
const glyph_bitmap = glyph.bitmap();
const buffer = glyph_bitmap.buffer();
const width = glyph_bitmap.width();
const height = glyph_bitmap.rows();
const margin = 1;
if (buffer == null) return RenderedGlyph{
.bitmap = null,
.width = width + (margin * 2),
.height = height + (margin * 2),
};
// Add 1 pixel padding to texture to avoid bleeding over other textures. This is part of the
// render() API contract.
f.bitmap.clearRetainingCapacity();
const num_pixels = (width + (margin * 2)) * (height + (margin * 2));
// TODO: handle OOM here
f.bitmap.ensureTotalCapacity(allocator, num_pixels) catch return error.RenderError;
f.bitmap.resize(allocator, num_pixels) catch return error.RenderError;
for (f.bitmap.items, 0..) |*data, i| {
const x = i % (width + (margin * 2));
const y = i / (width + (margin * 2));
if (x < margin or x > (width + margin) or y < margin or y > (height + margin)) {
data.* = RGBA32{ .r = 0, .g = 0, .b = 0, .a = 0 };
} else {
const alpha = buffer.?[((y - margin) * width + (x - margin)) % buffer.?.len];
data.* = RGBA32{ .r = 0, .g = 0, .b = 0, .a = alpha };
}
}
return RenderedGlyph{
.bitmap = f.bitmap.items,
.width = width + (margin * 2),
.height = height + (margin * 2),
};
}
pub fn deinit(f: *Font, allocator: std.mem.Allocator) void {
f.face.deinit();
f.bitmap.deinit(allocator);
}