define {Int,Float}Rect in terms of offset and extent

src/global.h

@@ -72,6 +72,10 @@ enum {
 	GAMEOVER_SCORE_DELAY = 60,
 };
 
+#define VIEWPORT_OFFSET { VIEWPORT_X, VIEWPORT_Y }
+#define VIEWPORT_SIZE { VIEWPORT_W, VIEWPORT_H }
+#define VIEWPORT_RECT { VIEWPORT_X, VIEWPORT_Y, VIEWPORT_W, VIEWPORT_H }
+
 typedef enum GameoverType {
 	GAMEOVER_NONE,
 	GAMEOVER_DEFEAT = 1,

src/util/geometry.h

@@ -11,18 +11,42 @@
 
 #include "taisei.h"
 
+typedef struct FloatOffset {
+	float x, y;
+} FloatOffset;
+
+typedef struct FloatExtent {
+	float w, h;
+} FloatExtent;
+
 typedef struct FloatRect {
-	float x;
-	float y;
-	float w;
-	float h;
+	union {
+		FloatOffset offset;
+		struct { float x, y; };
+	};
+	union {
+		FloatExtent extent;
+		struct { float w, h; };
+	};
 } FloatRect;
 
+typedef struct IntOffset {
+	int x, y;
+} IntOffset;
+
+typedef struct IntExtent {
+	int w, h;
+} IntExtent;
+
 typedef struct IntRect {
-	int x;
-	int y;
-	int w;
-	int h;
+	union {
+		IntOffset offset;
+		struct { int x, y; };
+	};
+	union {
+		IntExtent extent;
+		struct { int w, h; };
+	};
 } IntRect;
 
 typedef struct Ellipse {

src/video.h

@@ -28,6 +28,8 @@ enum {
 	SCREEN_H = 600,
 };
 
+#define SCREEN_SIZE { SCREEN_W, SCREEN_H }
+
 typedef struct VideoMode {
 	int width;
 	int height;