gentoo-overlay/app-text/xournal/files/xournal-0.4.5_p20111022-aspectratio.patch

https://sourceforge.net/tracker/?func=detail&aid=3082301&group_id=163434&atid=827735
To make the image patch even more useful, I've written this patch to allow the aspect ratio 
to be preserved when resizing selections. (It doesn't just apply to images.) Simply resize using the right 
mouse button (button-3) rather than the left mouse button.
This patch should be applied after the enhanced image patch. (Though it'd be easy enough to make the
changes to the raw 0.4.5 source directly since it doesn't change any of the image patch related areas.)
David Barton ( db9052 ) - 2010-10-06 09:30:56 PDT

diff -ur xournal-0.4.5/src/xo-paint.c xournal-0.4.5-aspectratio/src/xo-paint.c
--- xournal-0.4.5/src/xo-paint.c	2010-10-06 16:45:01.000000000 +0100
+++ xournal-0.4.5-aspectratio/src/xo-paint.c	2010-10-06 17:10:19.000000000 +0100
@@ -609,6 +609,12 @@
     ui.selection->new_x2 = ui.selection->bbox.right;
     gnome_canvas_item_set(ui.selection->canvas_item, "dash", NULL, NULL);
     update_cursor_for_resize(pt);
+
+    // Check whether we should preserve the aspect ratio
+    if (event->button.button == 3)
+    	ui.cur_brush->tool_options |= TOOLOPT_SELECT_PRESERVE;
+    else
+    	ui.cur_brush->tool_options &= ~TOOLOPT_SELECT_PRESERVE;
     return TRUE;
   }
   return FALSE;
@@ -740,6 +746,38 @@
   if (ui.selection->resizing_left) ui.selection->new_x1 = pt[0];
   if (ui.selection->resizing_right) ui.selection->new_x2 = pt[0];
 
+  if (ui.cur_brush->tool_options & TOOLOPT_SELECT_PRESERVE) {
+	  double aspectratio = (ui.selection->bbox.top - ui.selection->bbox.bottom)/(ui.selection->bbox.right - ui.selection->bbox.left);
+	  double newheight = ui.selection->new_y1 - ui.selection->new_y2;
+	  double newwidth = ui.selection->new_x2 - ui.selection->new_x1;
+	  gboolean boundheight;
+
+	  // Resizing from top or bottom only
+	  if ((ui.selection->resizing_top || ui.selection->resizing_bottom) && !(ui.selection->resizing_left || ui.selection->resizing_right))
+		  boundheight = 0;
+	  // Resizing from right or left only
+	  else if (!(ui.selection->resizing_top || ui.selection->resizing_bottom) && (ui.selection->resizing_left || ui.selection->resizing_right))
+		  boundheight = 1;
+	  // Resizing from a corner
+	  else if (newheight/aspectratio > newwidth)
+		  boundheight = 0;
+	  else
+		  boundheight = 1;
+
+	  if (boundheight) {
+		  // Bound the height
+		  newheight = newwidth*aspectratio;
+		  if (ui.selection->resizing_top) ui.selection->new_y1 = ui.selection->new_y2 + newheight;
+		  else ui.selection->new_y2 = ui.selection->new_y1 - newheight;
+	  }
+	  else {
+		  // Bound the width
+		  newwidth = newheight/aspectratio;
+		  if (ui.selection->resizing_left) ui.selection->new_x1 = ui.selection->new_x2 - newwidth;
+		  else ui.selection->new_x2 = ui.selection->new_x1 + newwidth;
+	  }
+  }
+
   gnome_canvas_item_set(ui.selection->canvas_item, 
     "x1", ui.selection->new_x1, "x2", ui.selection->new_x2,
     "y1", ui.selection->new_y1, "y2", ui.selection->new_y2, NULL);
diff -ur xournal-0.4.5/src/xournal.h xournal-0.4.5-aspectratio/src/xournal.h
--- xournal-0.4.5/src/xournal.h	2010-10-06 16:45:01.000000000 +0100
+++ xournal-0.4.5-aspectratio/src/xournal.h	2010-10-06 16:31:07.000000000 +0100
@@ -130,6 +130,7 @@
 #define TOOLOPT_ERASER_STANDARD     0
 #define TOOLOPT_ERASER_WHITEOUT     1
 #define TOOLOPT_ERASER_STROKES      2
+#define TOOLOPT_SELECT_PRESERVE     1 // Preserve the aspect ratio of the selection when resizing
 
 extern double predef_thickness[NUM_STROKE_TOOLS][THICKNESS_MAX];