add option to use 32-bit draw index (#4)

Author: Jack-Ji

build.zig

@@ -50,6 +50,11 @@ pub fn build(b: *std.Build) void {
             "use_wchar32",
             "Extended unicode support",
         ) orelse false,
+        .use_32bit_draw_idx = b.option(
+            bool,
+            "use_32bit_draw_idx",
+            "Use 32-bit draw index",
+        ) orelse false,
     };
 
     const options_step = b.addOptions();
@@ -66,7 +71,12 @@ pub fn build(b: *std.Build) void {
         },
     });
 
-    const cflags = &.{ "-fno-sanitize=undefined", "-Wno-elaborated-enum-base", "-Wno-error=date-time" };
+    const cflags = &.{
+        "-fno-sanitize=undefined",
+        "-Wno-elaborated-enum-base",
+        "-Wno-error=date-time",
+        if (options.use_32bit_draw_idx) "-DIMGUI_USE_32BIT_DRAW_INDEX" else "",
+    };
 
     const imgui = if (options.shared) blk: {
         const lib = b.addSharedLibrary(.{

libs/imgui/imconfig.h

@@ -111,7 +111,9 @@
 // Your renderer backend will need to support it (most example renderer backends support both 16/32-bit indices).
 // Another way to allow large meshes while keeping 16-bit indices is to handle ImDrawCmd::VtxOffset in your renderer.
 // Read about ImGuiBackendFlags_RendererHasVtxOffset for details.
-//#define ImDrawIdx unsigned int
+#ifdef IMGUI_USE_32BIT_DRAW_INDEX
+#define ImDrawIdx unsigned int
+#endif
 
 //---- Override ImDrawCallback signature (will need to modify renderer backends accordingly)
 //struct ImDrawList;

src/gui.zig

@@ -25,7 +25,7 @@ const assert = std.debug.assert;
 pub const f32_min: f32 = 1.17549435082228750796873653722225e-38;
 pub const f32_max: f32 = 3.40282346638528859811704183484517e+38;
 //--------------------------------------------------------------------------------------------------
-pub const DrawIdx = u16;
+pub const DrawIdx = if (@import("zgui_options").use_32bit_draw_idx) u32 else u16;
 pub const DrawVert = extern struct {
     pos: [2]f32,
     uv: [2]f32,