Graphics namespace includes rectangle, rounded rectangle, and circle

Also added methods to make writing to shm pool easier

src/graphics/mod.rs

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+
+pub mod rectangle;

src/graphics/rectangle.rs

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+
+use crate::wayland::shm::ShmPool;
+
+// l_row means local row and g_row means global row
+impl ShmPool {
+
+    // x and y are topleft corner of rect
+    pub fn rectangle(&mut self, x: usize, y: usize, w: usize, h: usize, color: u32) {
+        for g_row in y..y+h {
+            self.write(&vec![color; w], g_row*self.width+x);
+        }
+    }
+
+    // x and y and topleft corner of rect
+    pub fn rounded_rectangle(
+        &mut self,
+        x:      usize,
+        y:      usize,
+        w:      usize,
+        h:      usize,
+        radius: usize,
+        color:  u32
+    ) {
+        for l_row in 0..radius+1 {
+            let x_diff = radius - ((radius*radius - l_row*l_row) as f64).sqrt() as usize;
+            self.write(&vec![color; w - (2*x_diff)], (y+radius-l_row)*self.width + x + x_diff);
+            self.write(&vec![color; w - (2*x_diff)], (y+h-radius+l_row)*self.width + x + x_diff);
+        }
+        for g_row in y+radius..y+h-radius {
+            self.write(&vec![color; w], g_row*self.width+x);
+        }
+    }
+    
+    // x and y are center of circle
+    pub fn circle(&mut self, x: usize, y: usize, radius: usize, color: u32) {
+        for l_row in 0..radius { 
+            let x_diff = ((radius*radius - l_row*l_row) as f64).sqrt();
+            let mut row: Vec<u32> = vec![color; 2*x_diff as usize];
+            self.write(&row, (y+l_row)*self.width + x - x_diff as usize);
+            self.write(&row, (y-l_row)*self.width + x - x_diff as usize);
+        }
+    }
+}