Add action to toggle zoom keeping

Default key is Alt+z.

Relates to #240.

Signed-off-by: Artem Senichev <artemsen@gmail.com>

extra/swayimgrc

@@ -170,6 +170,7 @@ Shift+z = zoom fill
 0 = zoom real
 BackSpace = zoom optimal
 Alt+s = scale
+Alt+z = keep_zoom
 bracketleft = rotate_left
 bracketright = rotate_right
 m = flip_vertical

extra/swayimgrc.5

@@ -326,6 +326,7 @@ Predefined names for mouse scroll:
 .IP "\fBstep_down\fR \fI[PERCENT]\fR: move viewport down, default is 10%;"
 .IP "\fBzoom\fR \fI[SCALE]\fR: zoom in/out/fix, \fISCALE\fR is one of \fIviewer.scale\fR modes, or percent, e.g. \fI+10\fR;"
 .IP "\fBscale\fR \fI[SCALE]\fR: set default/global scale, \fISCALE\fR is one of \fIviewer.scale\fR modes, cycles through available modes by default;"
+.IP "\fBkeep_zoom\fR: toggle zoom keeping mode;"
 .IP "\fBrotate_left\fR: rotate image anticlockwise;"
 .IP "\fBrotate_right\fR: rotate image clockwise;"
 .IP "\fBflip_vertical\fR: flip image vertically;"

src/action.c

@@ -39,6 +39,7 @@ static const char* action_names[] = {
     [action_page_down] = "page_down",
     [action_zoom] = "zoom",
     [action_scale] = "scale",
+    [action_keep_zoom] = "keep_zoom",
     [action_rotate_left] = "rotate_left",
     [action_rotate_right] = "rotate_right",
     [action_flip_vertical] = "flip_vertical",

src/action.h

@@ -33,6 +33,7 @@ enum action_type {
     action_page_down,
     action_zoom,
     action_scale,
+    action_keep_zoom,
     action_rotate_left,
     action_rotate_right,
     action_flip_vertical,

src/config.c

@@ -107,6 +107,7 @@ static const struct config_default defaults[] = {
     { CFG_KEYS_VIEWER,  "Shift+z",          "zoom fill"              },
     { CFG_KEYS_VIEWER,  "0",                "zoom real"              },
     { CFG_KEYS_VIEWER,  "BackSpace",        "zoom optimal"           },
+    { CFG_KEYS_VIEWER,  "Alt+z",            "keep_zoom"              },
     { CFG_KEYS_VIEWER,  "bracketleft",      "rotate_left"            },
     { CFG_KEYS_VIEWER,  "bracketright",     "rotate_right"           },
     { CFG_KEYS_VIEWER,  "m",                "flip_vertical"          },

src/viewer.c

@@ -386,6 +386,16 @@ static void scale_global(const char* params)
     app_redraw();
 }
 
+/**
+ * Toggle zoom keeping mode.
+ */
+static void toggle_keep_zoom(void)
+{
+    ctx.keep_zoom = !ctx.keep_zoom;
+    info_update(info_status, "Keep zoom %s", ctx.keep_zoom ? "ON" : "OFF");
+    app_redraw();
+}
+
 /**
  * Start/stop animation if image supports it.
  * @param enable state to set
@@ -708,6 +718,9 @@ static void apply_action(const struct action* action)
         case action_scale:
             scale_global(action->params);
             break;
+        case action_keep_zoom:
+            toggle_keep_zoom();
+            break;
         case action_rotate_left:
             rotate_image(false);
             break;