Add customisable image resizing behaviour

Two new flags: -w and -W enable resizing and recentering, respectively.
Also add an 'autoresize' config variable to control this behaviour.

Fixes #122

3 files changed, 60 insertions, 1 deletions

diff --git a/doc/imv.1.txt b/doc/imv.1.txt
index 07167fd..6c2b45c 100644
--- a/doc/imv.1.txt
+++ b/doc/imv.1.txt
@@ -60,6 +60,12 @@ Options
 *-u* <linear|nearest_neighbour>::
 	Set upscaling method used by imv.
 
+*-w*::
+	Enable automatic resizing of the window to fit each image.
+
+*-W*::
+	Enable automatic resizing and recentering of the window to fit each image.
+
 *-x*::
 	Disable looping of input paths.
 
diff --git a/doc/imv.5.txt b/doc/imv.5.txt
index 36be08d..e323995 100644
--- a/doc/imv.5.txt
+++ b/doc/imv.5.txt
@@ -24,6 +24,11 @@ Options
 
 The *[options]* section accepts the following settings:
 
+*autoresize* = <none|resize|recenter>::
+	Sets the resizing behaviour when changing image. 'none' does nothing, and
+	is the default. 'resize' will resize the window to fit the image.
+	'recenter' will resize and recenter the window.
+
 *background* = <hex-code|'checks'>::
 	Set the background in imv. Can either be a 6-digit hexadecimal colour code,
 	or 'checks' for a chequered background. Defaults to '000000'
diff --git a/src/imv.c b/src/imv.c
index 2af5878..29e3a20 100644
--- a/src/imv.c
+++ b/src/imv.c
@@ -53,6 +53,13 @@ enum background_type {
   BACKGROUND_TYPE_COUNT
 };
 
+/* window behaviour on image change */
+enum resize_mode {
+  RESIZE_NONE,  /* do nothing */
+  RESIZE_ONLY,  /* resize to fit the new image */
+  RESIZE_CENTER /* resize to fit the new image and recenter */
+};
+
 struct backend_chain {
   const struct imv_backend *backend;
   struct backend_chain *next;
@@ -84,6 +91,10 @@ struct imv {
   /* dirty state flags */
   bool need_redraw;
   bool need_rescale;
+  bool need_resize;
+
+  /* mode for resizing the window on image change */
+  enum resize_mode resize_mode;
 
   /* traverse sub-directories for more images */
   bool recursive_load;
@@ -555,6 +566,26 @@ static bool parse_upscaling_method(struct imv *imv, const char *method)
   return false;
 }
 
+static bool parse_resizing_mode(struct imv *imv, const char *method)
+{
+  if (!strcmp(method, "none")) {
+    imv->upscaling_method = RESIZE_NONE;
+    return true;
+  }
+
+  if (!strcmp(method, "resize")) {
+    imv->upscaling_method = RESIZE_ONLY;
+    return true;
+  }
+
+  if (!strcmp(method, "recenter")) {
+    imv->upscaling_method = RESIZE_CENTER;
+    return true;
+  }
+
+  return false;
+}
+
 static int load_paths_from_stdin(void *data)
 {
   struct imv *imv = data;
@@ -613,11 +644,13 @@ bool imv_parse_args(struct imv *imv, int argc, char **argv)
 
   int o;
 
-  while((o = getopt(argc, argv, "frdxhlu:s:n:b:t:")) != -1) {
+  while((o = getopt(argc, argv, "frdwWxhlu:s:n:b:t:")) != -1) {
     switch(o) {
       case 'f': imv->fullscreen = true;                          break;
       case 'r': imv->recursive_load = true;                      break;
       case 'd': imv->overlay_enabled = true;                     break;
+      case 'w': imv->resize_mode = RESIZE_ONLY;                  break;
+      case 'W': imv->resize_mode = RESIZE_CENTER;                break;
       case 'x': imv->loop_input = false;                         break;
       case 'l': imv->list_files_at_exit = true;                  break;
       case 'n': imv->starting_path = optarg;                     break;
@@ -986,6 +1019,17 @@ static void handle_new_image(struct imv *imv, struct imv_bitmap *bitmap, int fra
   imv_bitmap_free(bitmap);
   imv->need_redraw = true;
   imv->need_rescale = true;
+  /* If autoresizing on every image is enabled, make sure we do so */
+  if (imv->resize_mode != RESIZE_NONE) {
+    imv->need_resize = true;
+  }
+  if (imv->need_resize) {
+    imv->need_resize = false;
+    SDL_SetWindowSize(imv->window, imv->current_image.width, imv->current_image.height);
+    if (imv->resize_mode == RESIZE_CENTER) {
+      SDL_SetWindowPosition(imv->window, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED);
+    }
+  }
   imv->loading = false;
   imv->next_frame_due = frametime ? SDL_GetTicks() + frametime : 0;
   imv->next_frame_duration = 0;
@@ -1282,6 +1326,10 @@ static int handle_ini_value(void *user, const char *section, const char *name,
       return 1;
     }
 
+    if(!strcmp(name, "autoresize")) {
+      return parse_resizing_mode(imv, value);
+    }
+
     if(!strcmp(name, "upscaling_method")) {
       return parse_upscaling_method(imv, value);
     }