Preserve panning when switching images; fixes issue #131

Makefile

@@ -1,4 +1,4 @@
-VERSION = git-20140202
+VERSION = git-20140204
 
 PREFIX    = /usr/local
 MANPREFIX = $(PREFIX)/share/man

commands.c

@@ -433,14 +433,12 @@ cmdreturn_t i_set_zoom(arg_t a)
 
 cmdreturn_t i_fit_to_win(arg_t a)
 {
-	cmdreturn_t ret = CMD_INVALID;
 	scalemode_t sm = (scalemode_t) a;
 
-	if (mode == MODE_IMAGE) {
-		if ((ret = img_fit_win(&img, sm)))
-			img_center(&img);
-	}
-	return ret;
+	if (mode == MODE_IMAGE)
+		return img_fit_win(&img, sm);
+	else
+		return CMD_INVALID;
 }
 
 cmdreturn_t i_fit_to_img(arg_t a)

image.c

@@ -334,8 +334,7 @@ bool img_load(img_t *img, const fileinfo_t *file)
 	img->w = imlib_image_get_width();
 	img->h = imlib_image_get_height();
 	img->scalemode = options->scalemode;
-	img->re = false;
-	img->checkpan = false;
+	img->checkpan = true;
 	img->dirty = true;
 
 	return true;
@@ -372,30 +371,29 @@ void img_check_pan(img_t *img, bool moved)
 {
 	win_t *win;
 	int ox, oy;
+	float w, h;
 
 	if (img == NULL || img->im == NULL || img->win == NULL)
 		return;
 
 	win = img->win;
+	w = img->w * img->zoom;
+	h = img->h * img->zoom;
 	ox = img->x;
 	oy = img->y;
 
-	if (img->w * img->zoom > win->w) {
-		if (img->x > 0 && img->x + img->w * img->zoom > win->w)
-			img->x = 0;
-		if (img->x < 0 && img->x + img->w * img->zoom < win->w)
-			img->x = win->w - img->w * img->zoom;
-	} else {
-		img->x = (win->w - img->w * img->zoom) / 2;
-	}
-	if (img->h * img->zoom > win->h) {
-		if (img->y > 0 && img->y + img->h * img->zoom > win->h)
-			img->y = 0;
-		if (img->y < 0 && img->y + img->h * img->zoom < win->h)
-			img->y = win->h - img->h * img->zoom;
-	} else {
-		img->y = (win->h - img->h * img->zoom) / 2;
-	}
+	if (w < win->w)
+		img->x = (win->w - w) / 2;
+	else if (img->x > 0)
+		img->x = 0;
+	else if (img->x + w < win->w)
+		img->x = win->w - w;
+	if (h < win->h)
+		img->y = (win->h - h) / 2;
+	else if (img->y > 0)
+		img->y = 0;
+	else if (img->y + h < win->h)
+		img->y = win->h - h;
 
 	if (!moved && (ox != img->x || oy != img->y))
 		img->dirty = true;
@@ -450,19 +448,6 @@ void img_render(img_t *img)
 	win = img->win;
 	img_fit(img);
 
-	if (!img->re) {
-		/* rendered for the first time */
-		img->re = true;
-		if (img->zoom * img->w <= win->w)
-			img->x = (win->w - img->w * img->zoom) / 2;
-		else
-			img->x = 0;
-		if (img->zoom * img->h <= win->h)
-			img->y = (win->h - img->h * img->zoom) / 2;
-		else
-			img->y = 0;
-	}
-
 	if (img->checkpan) {
 		img_check_pan(img, false);
 		img->checkpan = false;
@@ -511,28 +496,18 @@ void img_render(img_t *img)
 
 bool img_fit_win(img_t *img, scalemode_t sm)
 {
-	if (img == NULL || img->im == NULL)
-		return false;
-
-	img->scalemode = sm;
-	return img_fit(img);
-}
-
-bool img_center(img_t *img)
-{
-	int ox, oy;
+	float oz;
 
 	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
-
-	ox = img->x;
-	oy = img->y;
 
-	img->x = (img->win->w - img->w * img->zoom) / 2;
-	img->y = (img->win->h - img->h * img->zoom) / 2;
-
-	if (ox != img->x || oy != img->y) {
-		img->dirty = true;
+	oz = img->zoom;
+	img->scalemode = sm;
+
+	if (img_fit(img)) {
+		img->x = img->win->w / 2 - (img->win->w / 2 - img->x) * img->zoom / oz;
+		img->y = img->win->h / 2 - (img->win->h / 2 - img->y) * img->zoom / oz;
+		img->checkpan = true;
 		return true;
 	} else {
 		return false;

image.h

@@ -76,7 +76,6 @@ void img_close(img_t*, bool);
 void img_render(img_t*);
 
 bool img_fit_win(img_t*, scalemode_t);
-bool img_center(img_t*);
 
 bool img_zoom(img_t*, float);
 bool img_zoom_in(img_t*);