image: Combine clamp_view() and center_view ()

We need to clamp or center on a per axis basis.  If the window is wider
but the image is taller, we need to center horizontally but
clamp vertically.  We can only do that if by combining the two
functions.

clients/image.c

@@ -69,17 +69,6 @@ get_scale(struct image *image)
 	return image->matrix.xx;
 }
 
-static void
-center_view(struct image *image)
-{
-	struct rectangle allocation;
-	double scale = get_scale(image);
-
-	widget_get_allocation(image->widget, &allocation);
-	image->matrix.x0 = (allocation.width - image->width * scale) / 2;
-	image->matrix.y0 = (allocation.height - image->height * scale) / 2;
-}
-
 static void
 clamp_view(struct image *image)
 {
@@ -91,14 +80,25 @@ clamp_view(struct image *image)
 	sh = image->height * scale;
 	widget_get_allocation(image->widget, &allocation);
 
-	if (image->matrix.x0 > 0.0)
-		image->matrix.x0 = 0.0;
-	if (image->matrix.y0 > 0.0)
-		image->matrix.y0 = 0.0;
-	if (sw + image->matrix.x0 < allocation.width)
-		image->matrix.x0 = allocation.width - sw;
-	if (sh + image->matrix.y0 < allocation.height)
-		image->matrix.y0 = allocation.height - sh;
+	if (sw < allocation.width) {
+		image->matrix.x0 =
+			(allocation.width - image->width * scale) / 2;
+	} else {
+		if (image->matrix.x0 > 0.0)
+			image->matrix.x0 = 0.0;
+		if (sw + image->matrix.x0 < allocation.width)
+			image->matrix.x0 = allocation.width - sw;
+	}
+
+	if (sh < allocation.width) {
+		image->matrix.y0 =
+			(allocation.height - image->height * scale) / 2;
+	} else {
+		if (image->matrix.y0 > 0.0)
+			image->matrix.y0 = 0.0;
+		if (sh + image->matrix.y0 < allocation.height)
+			image->matrix.y0 = allocation.height - sh;
+	}
 }
 
 static void
@@ -141,7 +141,7 @@ redraw_handler(struct widget *widget, void *data)
 		image->height = height;
 		cairo_matrix_init_scale(&image->matrix, scale, scale);
 
-		center_view(image);
+		clamp_view(image);
 	}
 
 	matrix = image->matrix;
@@ -166,7 +166,7 @@ resize_handler(struct widget *widget,
 {
 	struct image *image = data;
 
-	center_view(image);
+	clamp_view(image);
 }
 
 static void
@@ -196,18 +196,6 @@ enter_handler(struct widget *widget,
 	return 1;
 }
 
-static bool
-image_is_smaller(struct image *image)
-{
-	double scale;
-	struct rectangle allocation;
-
-	scale = get_scale(image);
-	widget_get_allocation(image->widget, &allocation);
-
-	return scale * image->width < allocation.width;
-}
-
 static void
 move_viewport(struct image *image, double dx, double dy)
 {
@@ -217,11 +205,7 @@ move_viewport(struct image *image, double dx, double dy)
 		return;
 
 	cairo_matrix_translate(&image->matrix, -dx/scale, -dy/scale);
-
-	if (image_is_smaller(image))
-		center_view(image);
-	else
-		clamp_view(image);
+	clamp_view(image);
 
 	window_schedule_redraw(image->window);
 }
@@ -288,8 +272,7 @@ zoom(struct image *image, double scale)
 	cairo_matrix_translate(&scale_matrix, -x, -y);
 
 	cairo_matrix_multiply(&image->matrix, &image->matrix, &scale_matrix);
-	if (image_is_smaller(image))
-		center_view(image);
+	clamp_view(image);
 }
 
 static void