Implemented panning

image.c

@@ -123,11 +123,13 @@ void img_render(img_t *img, win_t *win) {
 		/* center image in window */
 		img->x = (win->w - img->w * img->zoom) / 2;
 		img->y = (win->h - img->h * img->zoom) / 2;
-	} else {
+	} else if (img->cp) {
-		/* typically after zooming and panning */
+		/* only useful after zooming */
 		img_check_pan(img, win);
+		img->cp = 0;
 	}
 
+	/* calculate source and destination offsets */
 	if (img->x < 0) {
 		sx = -img->x / img->zoom;
 		sw = win->w / img->zoom;
@@ -172,6 +174,7 @@ int img_zoom(img_t *img, float z) {
 		img->x -= (img->w * z - img->w * img->zoom) / 2;
 		img->y -= (img->h * z - img->h * img->zoom) / 2;
 		img->zoom = z;
+		img->cp = 1;
 		return 1;
 	} else {
 		return 0;
@@ -205,3 +208,32 @@ int img_zoom_out(img_t *img) {
 
 	return 0;
 }
+
+int img_pan(img_t *img, win_t *win, pandir_t dir) {
+	int ox, oy;
+
+	if (!img || !win)
+		return 0;
+
+	ox = img->x;
+	oy = img->y;
+
+	switch (dir) {
+		case PAN_LEFT:
+			img->x += win->w / 5;
+			break;
+		case PAN_RIGHT:
+			img->x -= win->w / 5;
+			break;
+		case PAN_UP:
+			img->y += win->h / 5;
+			break;
+		case PAN_DOWN:
+			img->y -= win->h / 5;
+			break;
+	}
+
+	img_check_pan(img, win);
+
+	return ox != img->x || oy != img->y;
+}

image.h

@@ -27,9 +27,17 @@ enum scalemode {
 	SCALE_ZOOM
 };
 
+typedef enum pandir_e {
+	PAN_LEFT = 0,
+	PAN_RIGHT,
+	PAN_UP,
+	PAN_DOWN
+} pandir_t;
+
 typedef struct img_s {
 	float zoom;
 	unsigned char re;
+	unsigned char cp;
 	int x;
 	int y;
 	int w;
@@ -45,4 +53,6 @@ void img_render(img_t*, win_t*);
 int img_zoom_in(img_t*);
 int img_zoom_out(img_t*);
 
+int img_pan(img_t*, win_t*, pandir_t);
+
 #endif /* IMAGE_H */

main.c

@@ -108,13 +108,14 @@ void cleanup() {
 
 void on_keypress(XEvent *ev) {
 	char key;
-	int len;
 	KeySym keysym;
+	int changed;
 
 	if (!ev)
 		return;
 	
-	len = XLookupString(&ev->xkey, &key, 1, &keysym, NULL);
+	XLookupString(&ev->xkey, &key, 1, &keysym, NULL);
+	changed = 0;
 
 	switch (keysym) {
 		case XK_Escape:
@@ -122,49 +123,59 @@ void on_keypress(XEvent *ev) {
 			exit(2);
 		case XK_space:
 			key = 'n';
-			len = 1;
 			break;
 		case XK_BackSpace:
 			key = 'p';
-			len = 1;
 			break;
 	}
 
-	if (!len)
-		return;
-
 	switch (key) {
 		case 'q':
 			cleanup();
 			exit(0);
+
+		/* navigate through image list */
 		case 'n':
 			if (fileidx + 1 < filecnt) {
 				img_load(&img, filenames[++fileidx]);
-				img_render(&img, &win);
+				changed = 1;
-				update_title();
 			}
 			break;
 		case 'p':
 			if (fileidx > 0) {
 				img_load(&img, filenames[--fileidx]);
-				img_render(&img, &win);
+				changed = 1;
-				update_title();
 			}
 			break;
+
+		/* zooming */
 		case '+':
 		case '=':
-			if (img_zoom_in(&img)) {
+			changed = img_zoom_in(&img);
-				img_render(&img, &win);
-				update_title();
-			}
 			break;
 		case '-':
-			if (img_zoom_out(&img)) {
+			changed = img_zoom_out(&img);
+			break;
+
+		/* panning */
+		case 'h':
+			changed = img_pan(&img, &win, PAN_LEFT);
+			break;
+		case 'j':
+			changed = img_pan(&img, &win, PAN_DOWN);
+			break;
+		case 'k':
+			changed = img_pan(&img, &win, PAN_UP);
+			break;
+		case 'l':
+			changed = img_pan(&img, &win, PAN_RIGHT);
+			break;
+	}
+
+	if (changed) {
 		img_render(&img, &win);
 		update_title();
 	}
-			break;
-	}
 }
 
 void on_configurenotify(XEvent *ev) {