Transparency works now and my brain is too fried to explain why

src/graphics/drawable.rs

@@ -42,8 +42,8 @@ pub fn color_over(over: u32, under: u32) -> u32 {
     let g_under = (under & 0x0000ff00) >> 8;
     let b_over  = (over  & 0x000000ff) >> 0;
     let b_under = (under & 0x000000ff) >> 0;
-    ((a_over + (a_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 24).min(0xff) +
-    ((r_over + (r_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 16).min(0xff) +
+    ((a_over + (a_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 24) +
+    ((r_over + (r_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 16) +
     ((g_over + (g_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 8) +
     ((b_over + (b_under as f64 * (0xff - a_over) as f64 / 0xff as f64) as u32).min(0xff) << 0)
 }

src/wayland/shm.rs

@@ -81,12 +81,34 @@ impl ShmPool {
         }}
     }
 
+    pub fn write_raw(&mut self, color: u32, offset: usize, len: usize) {
+        if offset + len/4 >= self.size {
+            return;
+        }
+        for i in offset..offset+len { unsafe {
+            *((self.addr as *mut u32).offset(i as isize)) = color;
+        }}
+    }
+
     pub fn write_pixel(&mut self, color: u32, offset: usize) {
         // TODO: Return error if out of bounds
         if offset + 3 > self.size {
             return;
         }
-        unsafe {*((self.addr as *mut u32).offset(offset as isize)) = color;}
+        unsafe {
+            *((self.addr as *mut u32).offset(offset as isize)) 
+            = color_over(color, self.read_pixel(offset).unwrap());
+        }
+    }
+
+    pub fn write_pixel_raw(&mut self, color: u32, offset: usize) {
+        // TODO: Return error if out of bounds
+        if offset + 3 > self.size {
+            return;
+        }
+        unsafe {
+            *((self.addr as *mut u32).offset(offset as isize)) = color;
+        }
     }
 
     pub fn read_pixel(&self, offset: usize) -> Option<u32> {

src/wayland/surface.rs

@@ -121,7 +121,7 @@ impl WlClient {
         self.wl_surface_attach(buffer)?;
         let mut drawables = self.drawables.lock()?;
         let mut shm_pool = self.shm_pool.lock()?;
-        shm_pool.write(0, 0, 800 * 800 * 2);
+        shm_pool.write_raw(0, 0, 800 * 800 * 2);
         for drawable in &mut *drawables {
             drawable.update();
             drawable.draw(buffer, &mut *shm_pool);

src/wayland/wl_client.rs

@@ -67,7 +67,7 @@ impl WlClient {
         arc_wl_client.wl_display_get_registry();
         if let Ok(mut drawables) = arc_wl_client.drawables.lock() {
             drawables.push(Rectangle::new(50, 50, 300, 300, 16, 0xffff8800).into());
-            drawables.push(Rectangle::new(350, 50, 300, 300, 16, 0xffaa22aa).into());
+            drawables.push(Rectangle::new(350, 50, 300, 300, 16, premultiply(0x77aa22aa)).into());
             drawables.push(Circle::new(350, 80, 25, premultiply(0xff00ffff)).into());
             drawables.push(Circle::new(350, 160, 25, premultiply(0x8800ffff)).into());
             drawables.push(Circle::new(350, 240, 25, premultiply(0x0000ffff)).into());