fix output scaling

We were applying the scale on the full output resolution. This fix
divides the current resolution by the scale, so that we later may
multiply it again to get the correct final image resolution.

daemon/src/wallpaper.rs

@@ -165,27 +165,49 @@ impl Wallpaper {
     #[inline]
     pub fn set_dimensions(&self, width: i32, height: i32) {
         let mut lock = self.inner_staging.lock().unwrap();
+        let scale = lock.scale_factor.get();
 
-        if width <= 0 {
-            error!("invalid width ({width}) for output: {:?}", self.output);
-        } else {
-            lock.width = unsafe { NonZeroI32::new_unchecked(width) };
+        match NonZeroI32::new(width / scale) {
+            Some(width) => lock.width = width,
+            None => {
+                error!("dividing width {width} by scale_factor {scale} results in width 0!")
+            }
         }
 
-        if height <= 0 {
-            error!("invalid height ({height}) for output: {:?}", self.output);
-        } else {
-            lock.height = unsafe { NonZeroI32::new_unchecked(height) };
+        match NonZeroI32::new(height / scale) {
+            Some(height) => lock.height = height,
+            None => {
+                error!("dividing height {height} by scale_factor {scale} results in height 0!")
+            }
         }
     }
 
     #[inline]
     pub fn set_scale(&self, scale: i32) {
         if scale <= 0 {
             error!("invalid scale ({scale}) for output: {:?}", self.output);
-        } else {
-            self.inner_staging.lock().unwrap().scale_factor =
-                unsafe { NonZeroI32::new_unchecked(scale) }
+            return;
+        }
+
+        let mut lock = self.inner_staging.lock().unwrap();
+        let (width, height) = (
+            lock.width.get() * lock.scale_factor.get(),
+            lock.height.get() * lock.scale_factor.get(),
+        );
+        lock.scale_factor = unsafe { NonZeroI32::new_unchecked(scale) };
+
+        match NonZeroI32::new(width / scale) {
+            Some(width) => lock.width = width,
+            None => {
+                error!("dividing width {width} by scale_factor {scale} results in width 0!")
+            }
+        }
+
+        match NonZeroI32::new(height / scale) {
+            Some(height) => lock.height = height,
+            None => {
+                error!("dividing height {height} by scale_factor {scale} results in height 0!")
+            }
         }
     }