From 231a2b63699a0e295b97e4126c772b950ec533ba Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Sat, 16 Dec 2023 20:11:37 -0800
Subject: [PATCH] renderer/opengl: implement fg_constrained

---
 src/renderer/Metal.zig              |  1 -
 src/renderer/OpenGL.zig             | 16 ++++++++++++----
 src/renderer/opengl/CellProgram.zig |  1 +
 src/renderer/shaders/cell.f.glsl    |  2 ++
 src/renderer/shaders/cell.v.glsl    | 15 ++++++++++++++-
 5 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/renderer/Metal.zig b/src/renderer/Metal.zig
index a3005751f..a606619ab 100644
--- a/src/renderer/Metal.zig
+++ b/src/renderer/Metal.zig
@@ -11,7 +11,6 @@ const objc = @import("objc");
 const macos = @import("macos");
 const imgui = @import("imgui");
 const glslang = @import("glslang");
-const ziglyph = @import("ziglyph");
 const apprt = @import("../apprt.zig");
 const configpkg = @import("../config.zig");
 const font = @import("../font/main.zig");
diff --git a/src/renderer/OpenGL.zig b/src/renderer/OpenGL.zig
index 61d3bd7fe..1cc16b060 100644
--- a/src/renderer/OpenGL.zig
+++ b/src/renderer/OpenGL.zig
@@ -9,6 +9,7 @@ const testing = std.testing;
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
 const link = @import("link.zig");
+const fgMode = @import("cell.zig").fgMode;
 const shadertoy = @import("shadertoy.zig");
 const apprt = @import("../apprt.zig");
 const configpkg = @import("../config.zig");
@@ -1489,10 +1490,17 @@ pub fn updateCell(
         );
 
         // If we're rendering a color font, we use the color atlas
-        const presentation = try self.font_group.group.presentationFromIndex(shaper_run.font_index);
-        const mode: CellProgram.CellMode = switch (presentation) {
-            .text => .fg,
-            .emoji => .fg_color,
+        const mode: CellProgram.CellMode = switch (try fgMode(
+            &self.font_group.group,
+            screen,
+            cell,
+            shaper_run,
+            x,
+            y,
+        )) {
+            .normal => .fg,
+            .color => .fg_color,
+            .constrained => .fg_constrained,
         };
 
         self.cells.appendAssumeCapacity(.{
diff --git a/src/renderer/opengl/CellProgram.zig b/src/renderer/opengl/CellProgram.zig
index 83bbbab72..1b51aa795 100644
--- a/src/renderer/opengl/CellProgram.zig
+++ b/src/renderer/opengl/CellProgram.zig
@@ -51,6 +51,7 @@ pub const Cell = extern struct {
 pub const CellMode = enum(u8) {
     bg = 1,
     fg = 2,
+    fg_constrained = 3,
     fg_color = 7,
     strikethrough = 8,
 
diff --git a/src/renderer/shaders/cell.f.glsl b/src/renderer/shaders/cell.f.glsl
index c261d03e5..e408fffc8 100644
--- a/src/renderer/shaders/cell.f.glsl
+++ b/src/renderer/shaders/cell.f.glsl
@@ -26,6 +26,7 @@ uniform vec2 cell_size;
 // See vertex shader
 const uint MODE_BG = 1u;
 const uint MODE_FG = 2u;
+const uint MODE_FG_CONSTRAINED = 3u;
 const uint MODE_FG_COLOR = 7u;
 const uint MODE_STRIKETHROUGH = 8u;
 
@@ -38,6 +39,7 @@ void main() {
         break;
 
     case MODE_FG:
+    case MODE_FG_CONSTRAINED:
         a = texture(text, glyph_tex_coords).r;
         vec3 premult = color.rgb * color.a;
         out_FragColor = vec4(premult.rgb*a, a);
diff --git a/src/renderer/shaders/cell.v.glsl b/src/renderer/shaders/cell.v.glsl
index bf35469db..18b586508 100644
--- a/src/renderer/shaders/cell.v.glsl
+++ b/src/renderer/shaders/cell.v.glsl
@@ -6,6 +6,7 @@
 // NOTE: this must be kept in sync with the fragment shader
 const uint MODE_BG = 1u;
 const uint MODE_FG = 2u;
+const uint MODE_FG_CONSTRAINED = 3u;
 const uint MODE_FG_COLOR = 7u;
 const uint MODE_STRIKETHROUGH = 8u;
 
@@ -179,6 +180,7 @@ void main() {
         break;
 
     case MODE_FG:
+    case MODE_FG_CONSTRAINED:
     case MODE_FG_COLOR:
         vec2 glyph_offset_calc = glyph_offset;
 
@@ -187,8 +189,19 @@ void main() {
         // So we flip it with `cell_size.y - glyph_offset.y`.
         glyph_offset_calc.y = cell_size_scaled.y - glyph_offset_calc.y;
 
+        // If this is a constrained mode, we need to constrain it!
+        vec2 glyph_size_calc = glyph_size;
+        if (mode == MODE_FG_CONSTRAINED) {
+            if (glyph_size.x > cell_size_scaled.x) {
+                float new_y = glyph_size.y * (cell_size_scaled.x / glyph_size.x);
+                glyph_offset_calc.y = glyph_offset_calc.y + (glyph_size.y - new_y);
+                glyph_size_calc.y = new_y;
+                glyph_size_calc.x = cell_size_scaled.x;
+            }
+        }
+
         // Calculate the final position of the cell.
-        cell_pos = cell_pos + (glyph_size * position) + glyph_offset_calc;
+        cell_pos = cell_pos + (glyph_size_calc * position) + glyph_offset_calc;
         gl_Position = projection * vec4(cell_pos, cell_z, 1.0);
 
         // We need to convert our texture position and size to normalized