use our built-in font for dev mode

pkg/imgui/font_atlas.zig

@@ -0,0 +1,34 @@
+const std = @import("std");
+const c = @import("c.zig");
+const imgui = @import("main.zig");
+const Allocator = std.mem.Allocator;
+
+pub const FontAtlas = opaque {
+    pub fn addFontFromMemoryTTF(
+        self: *FontAtlas,
+        data: []const u8,
+        size_px: f32,
+    ) void {
+        // We never want the data to be copied by the Atlas, its not
+        // very Zig-like, so we just always set this to false.
+        var cfg = c.ImFontConfig_ImFontConfig();
+        cfg.*.FontDataOwnedByAtlas = false;
+        defer c.ImFontConfig_destroy(cfg);
+
+        _ = c.ImFontAtlas_AddFontFromMemoryTTF(
+            self.cval(),
+            @intToPtr(?*anyopaque, @ptrToInt(data.ptr)),
+            @intCast(c_int, data.len),
+            size_px,
+            cfg,
+            null,
+        );
+    }
+
+    pub inline fn cval(self: *FontAtlas) *c.ImFontAtlas {
+        return @ptrCast(
+            *c.ImFontAtlas,
+            @alignCast(@alignOf(c.ImFontAtlas), self),
+        );
+    }
+};

pkg/imgui/main.zig

@@ -2,6 +2,7 @@ pub const c = @import("c.zig");
 pub usingnamespace @import("context.zig");
 pub usingnamespace @import("core.zig");
 pub usingnamespace @import("draw_data.zig");
+pub usingnamespace @import("font_atlas.zig");
 pub usingnamespace @import("io.zig");
 pub usingnamespace @import("style.zig");