From 05b87b1406d10a839a8864e13930f486f647fde4 Mon Sep 17 00:00:00 2001
From: Jonathan Marler <johnnymarler@gmail.com>
Date: Tue, 23 Sep 2025 13:32:13 -0600
Subject: [PATCH] finish win32 gui support for double-wide characters

---
 src/win32/DwriteRenderer.zig |  6 +++++-
 src/win32/d3d11.zig          | 20 ++++++++++++++++----
 src/win32/gui.zig            |  6 ++++--
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/win32/DwriteRenderer.zig b/src/win32/DwriteRenderer.zig
index 8ad34a0..39abee5 100644
--- a/src/win32/DwriteRenderer.zig
+++ b/src/win32/DwriteRenderer.zig
@@ -75,6 +75,7 @@ pub fn render(
     self: *const DwriteRenderer,
     font: Font,
     utf8: []const u8,
+    double_width: bool,
 ) void {
     var utf16_buf: [10]u16 = undefined;
     const utf16_len = std.unicode.utf8ToUtf16Le(&utf16_buf, utf8) catch unreachable;
@@ -85,7 +86,10 @@ pub fn render(
         const rect: win32.D2D_RECT_F = .{
             .left = 0,
             .top = 0,
-            .right = @floatFromInt(font.cell_size.x),
+            .right = if (double_width)
+                @as(f32, @floatFromInt(font.cell_size.x)) * @as(f32, @floatFromInt(font.cell_size.x))
+            else
+                @as(f32, @floatFromInt(font.cell_size.x)),
             .bottom = @floatFromInt(font.cell_size.y),
         };
         self.render_target.BeginDraw();
diff --git a/src/win32/d3d11.zig b/src/win32/d3d11.zig
index b1b88cf..dd1c5a2 100644
--- a/src/win32/d3d11.zig
+++ b/src/win32/d3d11.zig
@@ -149,7 +149,7 @@ pub const WindowState = struct {
     }
 
     // TODO: this should take a utf8 graphme instead
-    pub fn generateGlyph(state: *WindowState, font: Font, codepoint: u21, right_half: bool) u32 {
+    pub fn generateGlyph(state: *WindowState, font: Font, codepoint: u21, kind: enum { single, left, right }) u32 {
         // for now we'll just use 1 texture and leverage the entire thing
         const texture_cell_count: XY(u16) = getD3d11TextureMaxCellCount(font.cell_size);
         const texture_cell_count_total: u32 =
@@ -184,6 +184,11 @@ pub const WindowState = struct {
             break :blk &(state.glyph_index_cache.?);
         };
 
+        const right_half: bool = switch (kind) {
+            .single, .left => false,
+            .right => true,
+        };
+
         switch (glyph_index_cache.reserve(
             global.glyph_cache_arena.allocator(),
             codepoint,
@@ -194,8 +199,11 @@ pub const WindowState = struct {
                 // defer if (!render_success) state.glyph_index_cache.remove(reserved.index);
                 const pos: XY(u16) = cellPosFromIndex(reserved.index, texture_cell_count.x);
                 const coord = coordFromCellPos(font.cell_size, pos);
-                var staging_size = font.cell_size;
-                staging_size.x = if (right_half) staging_size.x * 2 else staging_size.x;
+                const staging_size: XY(u16) = .{
+                    // twice the width to handle double-wide glyphs
+                    .x = font.cell_size.x * 2,
+                    .y = font.cell_size.y,
+                };
                 const staging = global.staging_texture.update(staging_size);
                 var utf8_buf: [7]u8 = undefined;
                 const utf8_len: u3 = std.unicode.utf8Encode(codepoint, &utf8_buf) catch |e| std.debug.panic(
@@ -205,6 +213,10 @@ pub const WindowState = struct {
                 staging.text_renderer.render(
                     font,
                     utf8_buf[0..utf8_len],
+                    switch (kind) {
+                        .single => false,
+                        .left, .right => true,
+                    },
                 );
                 const box: win32.D3D11_BOX = .{
                     .left = if (right_half) font.cell_size.x else 0,
@@ -292,7 +304,7 @@ pub fn paint(
     }
 
     const copy_col_count: u16 = @min(col_count, shader_col_count);
-    const blank_space_glyph_index = state.generateGlyph(font, ' ', false);
+    const blank_space_glyph_index = state.generateGlyph(font, ' ', .single);
 
     const cell_count: u32 = @as(u32, shader_col_count) * @as(u32, shader_row_count);
     state.shader_cells.updateCount(cell_count);
diff --git a/src/win32/gui.zig b/src/win32/gui.zig
index 485d1b4..bab2196 100644
--- a/src/win32/gui.zig
+++ b/src/win32/gui.zig
@@ -1083,6 +1083,7 @@ fn WndProc(
             ) catch |e| oom(e);
             var prev_width: usize = 1;
             var prev_cell: render.Cell = undefined;
+            var prev_codepoint: u21 = undefined;
             for (global.screen.buf, global.render_cells.items) |*screen_cell, *render_cell| {
                 const width = screen_cell.char.width;
                 const codepoint = if (std.unicode.utf8ValidateSlice(screen_cell.char.grapheme))
@@ -1091,16 +1092,17 @@ fn WndProc(
                     std.unicode.replacement_character;
                 if (prev_width > 1) {
                     render_cell.* = prev_cell;
-                    render_cell.glyph_index = state.render_state.generateGlyph(font, codepoint, true);
+                    render_cell.glyph_index = state.render_state.generateGlyph(font, prev_codepoint, .right);
                 } else {
                     render_cell.* = .{
-                        .glyph_index = state.render_state.generateGlyph(font, codepoint, false),
+                        .glyph_index = state.render_state.generateGlyph(font, codepoint, if (width == 1) .single else .left),
                         .background = renderColorFromVaxis(screen_cell.style.bg),
                         .foreground = renderColorFromVaxis(screen_cell.style.fg),
                     };
                 }
                 prev_width = width;
                 prev_cell = render_cell.*;
+                prev_codepoint = codepoint;
             }
             render.paint(
                 &state.render_state,