"Better Glyph Constraint Logic" follow-up (#7822)

Follow-up to #7809, a handful of small fixes/improvements, explained
individually in each commit message.

> [!NOTE]
> Similar to the inverted "monochrome" ft flag fix from #7809, it was
pointed out that "force-autohint" was also inverted, so I did invert
that too, this has the same result of no impact on users who haven't
explicitly set it, but a breaking behavior change for users who have set
it. *These changes definitely need to be pointed out in the 1.2 release
notes!*

pkg/opengl/Texture.zig

@@ -92,6 +92,30 @@ pub const Format = enum(c_uint) {
     _,
 };
 
+/// Minification filter for textures.
+pub const MinFilter = enum(c_int) {
+    nearest = c.GL_NEAREST,
+    linear = c.GL_LINEAR,
+    nearest_mipmap_nearest = c.GL_NEAREST_MIPMAP_NEAREST,
+    linear_mipmap_nearest = c.GL_LINEAR_MIPMAP_NEAREST,
+    nearest_mipmap_linear = c.GL_NEAREST_MIPMAP_LINEAR,
+    linear_mipmap_linear = c.GL_LINEAR_MIPMAP_LINEAR,
+};
+
+/// Magnification filter for textures.
+pub const MagFilter = enum(c_int) {
+    nearest = c.GL_NEAREST,
+    linear = c.GL_LINEAR,
+};
+
+/// Texture coordinate wrapping mode.
+pub const Wrap = enum(c_int) {
+    clamp_to_edge = c.GL_CLAMP_TO_EDGE,
+    clamp_to_border = c.GL_CLAMP_TO_BORDER,
+    mirrored_repeat = c.GL_MIRRORED_REPEAT,
+    repeat = c.GL_REPEAT,
+};
+
 /// Data type for texture images.
 pub const DataType = enum(c_uint) {
     UnsignedByte = c.GL_UNSIGNED_BYTE,

src/config/Config.zig

@@ -435,7 +435,7 @@ pub const compatibility = std.StaticStringMap(
 ///   * `hinting` - Enable or disable hinting. Enabled by default.
 ///
 ///   * `force-autohint` - Always use the freetype auto-hinter instead of
-///     the font's native hinter. Enabled by default.
+///     the font's native hinter. Disabled by default.
 ///
 ///   * `monochrome` - Instructs renderer to use 1-bit monochrome rendering.
 ///     This will disable anti-aliasing, and probably not look very good unless
@@ -7084,7 +7084,7 @@ pub const FreetypeLoadFlags = packed struct {
     // for Freetype itself. Ghostty hasn't made any opinionated changes
     // to these defaults.
     hinting: bool = true,
-    @"force-autohint": bool = true,
+    @"force-autohint": bool = false,
     monochrome: bool = false,
     autohint: bool = true,
 };

src/font/face/coretext.zig

@@ -356,8 +356,14 @@ pub const Face = struct {
         const x = glyph_size.x;
         const y = glyph_size.y;
 
-        const px_width: u32 = @intFromFloat(@ceil(width));
+        // We have to include the fractional pixels that we won't be offsetting
-        const px_height: u32 = @intFromFloat(@ceil(height));
+        // in our width and height calculations, that is, we offset by the floor
+        // of the bearings when we render the glyph, meaning there's still a bit
+        // of extra width to the area that's drawn in beyond just the width of
+        // the glyph itself, so we include that extra fraction of a pixel when
+        // calculating the width and height here.
+        const px_width: u32 = @intFromFloat(@ceil(width + rect.origin.x - @floor(rect.origin.x)));
+        const px_height: u32 = @intFromFloat(@ceil(height + rect.origin.y - @floor(rect.origin.y)));
 
         // Settings that are specific to if we are rendering text or emoji.
         const color: struct {

src/font/face/freetype.zig

@@ -348,7 +348,7 @@ pub const Face = struct {
 
             // use options from config
             .no_hinting = !do_hinting,
-            .force_autohint = !self.load_flags.@"force-autohint",
+            .force_autohint = self.load_flags.@"force-autohint",
             .no_autohint = !self.load_flags.autohint,
 
             // NO_SVG set to true because we don't currently support rendering

src/font/sprite/canvas.zig

@@ -140,24 +140,7 @@ pub const Canvas = struct {
         const region_height = sfc_height -| self.clip_top -| self.clip_bottom;
 
         // Allocate our texture atlas region
-        const region = region: {
+        const region = try atlas.reserve(alloc, region_width, region_height);
-            // Reserve a region with a 1px margin on the bottom and right edges
-            // so that we can avoid interpolation between adjacent glyphs during
-            // texture sampling.
-            var region = try atlas.reserve(
-                alloc,
-                region_width + 1,
-                region_height + 1,
-            );
-
-            // Modify the region to remove the margin so that we write to the
-            // non-zero location. The data in an Altlas is always initialized
-            // to zero (Atlas.clear) so we don't need to worry about zero-ing
-            // that.
-            region.width -= 1;
-            region.height -= 1;
-            break :region region;
-        };
 
         if (region.width > 0 and region.height > 0) {
             const buffer: []u8 = @ptrCast(self.sfc.image_surface_alpha8.buf);

src/renderer/OpenGL.zig

@@ -356,6 +356,10 @@ pub inline fn textureOptions(self: OpenGL) Texture.Options {
         .format = .rgba,
         .internal_format = .srgba,
         .target = .@"2D",
+        .min_filter = .linear,
+        .mag_filter = .linear,
+        .wrap_s = .clamp_to_edge,
+        .wrap_t = .clamp_to_edge,
     };
 }
 
@@ -388,6 +392,16 @@ pub inline fn imageTextureOptions(
         .format = format.toPixelFormat(),
         .internal_format = if (srgb) .srgba else .rgba,
         .target = .@"2D",
+        // TODO: Generate mipmaps for image textures and use
+        //       linear_mipmap_linear filtering so that they
+        //       look good even when scaled way down.
+        .min_filter = .linear,
+        .mag_filter = .linear,
+        // TODO: Separate out background image options, use
+        //       repeating coordinate modes so we don't have
+        //       to do the modulus in the shader.
+        .wrap_s = .clamp_to_edge,
+        .wrap_t = .clamp_to_edge,
     };
 }
 
@@ -409,6 +423,10 @@ pub fn initAtlasTexture(
             .format = format,
             .internal_format = internal_format,
             .target = .Rectangle,
+            .min_filter = .nearest,
+            .mag_filter = .nearest,
+            .wrap_s = .clamp_to_edge,
+            .wrap_t = .clamp_to_edge,
         },
         atlas.size,
         atlas.size,

src/renderer/opengl/Texture.zig

@@ -16,6 +16,10 @@ pub const Options = struct {
     format: gl.Texture.Format,
     internal_format: gl.Texture.InternalFormat,
     target: gl.Texture.Target,
+    min_filter: gl.Texture.MinFilter,
+    mag_filter: gl.Texture.MagFilter,
+    wrap_s: gl.Texture.Wrap,
+    wrap_t: gl.Texture.Wrap,
 };
 
 texture: gl.Texture,
@@ -48,10 +52,10 @@ pub fn init(
     {
         const texbind = tex.bind(opts.target) catch return error.OpenGLFailed;
         defer texbind.unbind();
-        texbind.parameter(.WrapS, gl.c.GL_CLAMP_TO_EDGE) catch return error.OpenGLFailed;
+        texbind.parameter(.WrapS, @intFromEnum(opts.wrap_s)) catch return error.OpenGLFailed;
-        texbind.parameter(.WrapT, gl.c.GL_CLAMP_TO_EDGE) catch return error.OpenGLFailed;
+        texbind.parameter(.WrapT, @intFromEnum(opts.wrap_t)) catch return error.OpenGLFailed;
-        texbind.parameter(.MinFilter, gl.c.GL_LINEAR) catch return error.OpenGLFailed;
+        texbind.parameter(.MinFilter, @intFromEnum(opts.min_filter)) catch return error.OpenGLFailed;
-        texbind.parameter(.MagFilter, gl.c.GL_LINEAR) catch return error.OpenGLFailed;
+        texbind.parameter(.MagFilter, @intFromEnum(opts.mag_filter)) catch return error.OpenGLFailed;
         texbind.image2D(
             0,
             opts.internal_format,