add ScaleMode::Fill to fill screen without black borders

uw8-window/src/gpu/scale_mode.rs

@@ -0,0 +1,28 @@
+use winit::dpi::PhysicalSize;
+
+#[derive(Debug, Copy, Clone)]
+pub enum ScaleMode {
+    Fit,
+    Fill,
+}
+
+impl Default for ScaleMode {
+    fn default() -> ScaleMode {
+        ScaleMode::Fit
+    }
+}
+
+impl ScaleMode {
+    pub fn texture_scale_from_resolution(&self, res: PhysicalSize<u32>) -> [f32; 4] {
+        let scale = match self {
+            ScaleMode::Fit => ((res.width as f32) / 160.0).min((res.height as f32) / 120.0),
+            ScaleMode::Fill => ((res.width as f32) / 160.0).max((res.height as f32) / 120.0),
+        };
+        [
+            scale / res.width as f32,
+            scale / res.height as f32,
+            2.0 / scale,
+            0.0,
+        ]
+    }
+}