Add initial_pan option to set the starting pan position

3 files changed, 51 insertions, 2 deletions

diff --git a/src/imv.c b/src/imv.c
index d8f8304..b12ed98 100644
--- a/src/imv.c
+++ b/src/imv.c
@@ -114,6 +114,10 @@ struct imv {
   /* scale up / down images to match window, or actual size */
   enum scaling_mode scaling_mode;
 
+  /* initial pan factor when opening new images */
+  bool custom_start_pan;
+  double initial_pan_x, initial_pan_y;
+
   struct {
     /* show a solid background colour, or chequerboard pattern */
     enum background_type type;
@@ -670,6 +674,18 @@ static bool parse_upscaling_method(struct imv *imv, const char *method)
   return false;
 }
 
+static bool parse_initial_pan(struct imv *imv, const char *pan_params)
+{
+  char *next_val;
+  long int val_x = strtol(pan_params, &next_val, 10);
+  long int val_y = strtol(next_val, NULL, 10);
+
+  imv->custom_start_pan = true;
+  imv->initial_pan_x = (double)val_x / (double)100;
+  imv->initial_pan_y = (double)val_y / (double)100;
+  return true;
+}
+
 static void *load_paths_from_stdin(void *data)
 {
   struct imv *imv = data;
@@ -1064,6 +1080,10 @@ static bool setup_window(struct imv *imv)
     imv->view = imv_viewport_create(ww, wh, bw, bh);
   }
 
+  if (imv->custom_start_pan) {
+    imv_viewport_set_default_pan_factor(imv->view, imv->initial_pan_x, imv->initial_pan_y);
+  }
+
   /* put us in fullscren mode to begin with if requested */
   imv_window_set_fullscreen(imv->window, imv->start_fullscreen);
 
@@ -1319,6 +1339,10 @@ static int handle_ini_value(void *user, const char *section, const char *name,
       return parse_scaling_mode(imv, value);
     }
 
+    if (!strcmp(name, "initial_pan")) {
+      return parse_initial_pan(imv, value);
+    }
+
     if (!strcmp(name, "background")) {
       if (!parse_bg(imv, value)) {
         return false;
diff --git a/src/viewport.c b/src/viewport.c
index e04648f..ce9fa54 100644
--- a/src/viewport.c
+++ b/src/viewport.c
@@ -9,6 +9,7 @@ struct imv_viewport {
     int width, height;
   } buffer; /* rendering buffer dimensions */
   int x, y;
+  double pan_factor_x, pan_factor_y;
   int redraw;
   int playing;
   int locked;
@@ -30,6 +31,7 @@ struct imv_viewport *imv_viewport_create(int window_width, int window_height,
   view->buffer.height = buffer_height;
   view->scale = 1;
   view->x = view->y = view->redraw = 0;
+  view->pan_factor_x = view->pan_factor_y = 0.5;
   view->playing = 1;
   view->locked = 0;
   return view;
@@ -80,6 +82,12 @@ void imv_viewport_get_scale(struct imv_viewport *view, double *scale)
   }
 }
 
+void imv_viewport_set_default_pan_factor(struct imv_viewport *view, double pan_factor_x, double pan_factor_y)
+{
+  view->pan_factor_x = pan_factor_x;
+  view->pan_factor_y = pan_factor_y;
+}
+
 void imv_viewport_move(struct imv_viewport *view, int x, int y,
     const struct imv_image *image)
 {
@@ -172,8 +180,22 @@ void imv_viewport_center(struct imv_viewport *view, const struct imv_image *imag
   const int image_width = imv_image_width(image);
   const int image_height = imv_image_height(image);
 
-  view->x = (view->buffer.width - image_width * view->scale) / 2;
-  view->y = (view->buffer.height - image_height * view->scale) / 2;
+  view->x = view->buffer.width - image_width * view->scale;
+  view->y = view->buffer.height - image_height * view->scale;
+
+  if (view->x > 0) {
+    /* Image is smaller than the window. Center the image */
+    view->x *= 0.5;
+  } else {
+    view->x *= view->pan_factor_x;
+  }
+
+  if (view->y > 0) {
+    /* Image is smaller than the window. Center the image */
+    view->y *= 0.5;
+  } else {
+    view->y *= view->pan_factor_y;
+  }
 
   view->locked = 1;
   view->redraw = 1;
diff --git a/src/viewport.h b/src/viewport.h
index 32fc728..0b9519f 100644
--- a/src/viewport.h
+++ b/src/viewport.h
@@ -34,6 +34,9 @@ void imv_viewport_get_offset(struct imv_viewport *view, int *x, int *y);
 /* Fetch viewport scale */
 void imv_viewport_get_scale(struct imv_viewport *view, double *scale);
 
+/* Set the default pan_factor factor for the x and y position */
+void imv_viewport_set_default_pan_factor(struct imv_viewport *view, double pan_factor_x, double pan_factor_y);
+
 /* Pan the view by the given amounts without letting the image get too far
  * off-screen */
 void imv_viewport_move(struct imv_viewport *view, int x, int y,