minimal_zgui_glfw_gl: fix dpi scaling

Author: hazeycode

libs/zgui/src/backend_glfw_opengl.zig

@@ -22,10 +22,13 @@ pub fn deinit() void {
     ImGui_ImplOpenGL3_Shutdown();
 }
 
-pub fn newFrame() void {
+pub fn newFrame(fb_width: u32, fb_height: u32) void {
     ImGui_ImplGlfw_NewFrame();
     ImGui_ImplOpenGL3_NewFrame();
 
+    gui.io.setDisplaySize(@as(f32, @floatFromInt(fb_width)), @as(f32, @floatFromInt(fb_height)));
+    gui.io.setDisplayFramebufferScale(1.0, 1.0);
+
     gui.newFrame();
 }
 

samples/minimal_zgui_glfw_gl/src/minimal_zgui_glfw_gl.zig

@@ -43,11 +43,17 @@ pub fn main() !void {
     zgui.init(gpa);
     defer zgui.deinit();
 
+    const scale_factor = scale_factor: {
+        const scale = window.getContentScale();
+        break :scale_factor @max(scale[0], scale[1]);
+    };
     _ = zgui.io.addFontFromFile(
         content_dir ++ "Roboto-Medium.ttf",
-        std.math.floor(16.0),
+        std.math.floor(16.0 * scale_factor),
     );
 
+    zgui.getStyle().scaleAllSizes(scale_factor);
+
     zgui.backend.init(window);
     defer zgui.backend.deinit();
 
@@ -56,7 +62,9 @@ pub fn main() !void {
 
         gl.clearBufferfv(gl.COLOR, 0, &[_]f32{ 0, 0, 0, 1.0 });
 
-        zgui.backend.newFrame();
+        const fb_size = window.getFramebufferSize();
+
+        zgui.backend.newFrame(@intCast(fb_size[0]), @intCast(fb_size[1]));
 
         // Set the starting window position and size to custom values
         zgui.setNextWindowPos(.{ .x = 20.0, .y = 20.0, .cond = .first_use_ever });