[gthumb] rotate tool: locking the cropping region inside the rotated image

[Paolo Bacchilega <paobac src gnome org>]

commit ee29c42ee986cf9d604aab664186194dcde1fc9e
Author: Stefano Pettini <spettini users sourceforge net>
Date:   Sat Apr 30 23:07:49 2011 +0100

    rotate tool: locking the cropping region inside the rotated image

 extensions/file_tools/gdk-pixbuf-rotate.c    |   18 +++++++++++++++++-
 extensions/file_tools/gdk-pixbuf-rotate.h    |    3 ++-
 extensions/file_tools/gth-file-tool-rotate.c |   18 +++++++++++++-----
 3 files changed, 32 insertions(+), 7 deletions(-)
---
diff --git a/extensions/file_tools/gdk-pixbuf-rotate.c b/extensions/file_tools/gdk-pixbuf-rotate.c
index 3f59b4c..c0ad497 100644
--- a/extensions/file_tools/gdk-pixbuf-rotate.c
+++ b/extensions/file_tools/gdk-pixbuf-rotate.c
@@ -47,7 +47,8 @@
 void
 _gdk_pixbuf_rotate_get_cropping_parameters (GdkPixbuf *src_pixbuf,
 					    double     angle,
-					    double    *p1_plus_p2)
+					    double    *p1_plus_p2,
+					    double    *p_min)
 {
 	double angle_rad;
 	double cos_angle, sin_angle;
@@ -69,12 +70,16 @@ _gdk_pixbuf_rotate_get_cropping_parameters (GdkPixbuf *src_pixbuf,
 		t2 = sin_angle * src_width + cos_angle * src_height;
 
 		*p1_plus_p2  = 1.0 + (t1 * src_height) / (t2 * src_width);
+		
+		*p_min = src_height / src_width * sin_angle * cos_angle + (*p1_plus_p2 - 1) * cos_angle * cos_angle;
 	}
 	else {
 		t1 = cos_angle * src_height - sin_angle * src_width;
 		t2 = sin_angle * src_height + cos_angle * src_width;
 
 		*p1_plus_p2 = 1.0 + (t1 * src_width)  / (t2 * src_height);
+		
+		*p_min = src_width / src_height * sin_angle * cos_angle + (*p1_plus_p2 - 1) * cos_angle * cos_angle;
 	}
 }
 
@@ -105,6 +110,17 @@ _gdk_pixbuf_rotate_get_cropping_region (GdkPixbuf *src_pixbuf,
 	src_width  = gdk_pixbuf_get_width  (src_pixbuf) - 1;
 	src_height = gdk_pixbuf_get_height (src_pixbuf) - 1;
 
+	if (angle < 0) {
+
+		/* This is to make the p1/p2 sliders behavour more user friendly */
+
+		double t;
+
+		t = p1;
+		p1 = p2;
+		p2 = t;
+	}
+
 	if (src_width > src_height) {
 
 		xx1 = p1 * src_width * cos_angle + src_height * sin_angle;
diff --git a/extensions/file_tools/gdk-pixbuf-rotate.h b/extensions/file_tools/gdk-pixbuf-rotate.h
index c037e80..01db0e8 100644
--- a/extensions/file_tools/gdk-pixbuf-rotate.h
+++ b/extensions/file_tools/gdk-pixbuf-rotate.h
@@ -30,7 +30,8 @@ G_BEGIN_DECLS
 
 void _gdk_pixbuf_rotate_get_cropping_parameters (GdkPixbuf *src_pixbuf,
 					         double     angle,
-					         double    *p1_plus_p2);
+					         double    *p1_plus_p2,
+					         double    *p_min);
 
 void _gdk_pixbuf_rotate_get_cropping_region (GdkPixbuf    *src_pixbuf,
 					     double        angle,
diff --git a/extensions/file_tools/gth-file-tool-rotate.c b/extensions/file_tools/gth-file-tool-rotate.c
index 259ff0d..07419ac 100644
--- a/extensions/file_tools/gth-file-tool-rotate.c
+++ b/extensions/file_tools/gth-file-tool-rotate.c
@@ -69,6 +69,7 @@ update_crop_parameters (GthFileToolRotate *self)
 	double    rotation_angle;
 	gboolean  keep_aspect_ratio;
 	double    crop_p1;
+	double    crop_p_min;
 
 	window = gth_file_tool_get_window (GTH_FILE_TOOL (self));
 	viewer_page = gth_browser_get_viewer_page (GTH_BROWSER (window));
@@ -94,14 +95,18 @@ update_crop_parameters (GthFileToolRotate *self)
 
 			_gdk_pixbuf_rotate_get_cropping_parameters (self->priv->src_pixbuf,
 								    rotation_angle,
-								    &self->priv->crop_p1_plus_p2);
+								    &self->priv->crop_p1_plus_p2,
+								    &crop_p_min);
 
 			/* This centers the cropping region in the middle of the rotated image */
 
 			crop_p1 = self->priv->crop_p1_plus_p2 / 2.0;
 
-			gtk_adjustment_set_lower (self->priv->crop_p1_adj, MAX (self->priv->crop_p1_plus_p2 - 1, 0));
-			gtk_adjustment_set_lower (self->priv->crop_p2_adj, MAX (self->priv->crop_p1_plus_p2 - 1, 0));
+			gtk_adjustment_set_lower (self->priv->crop_p1_adj, MAX (crop_p_min, 0.0));
+			gtk_adjustment_set_lower (self->priv->crop_p2_adj, MAX (crop_p_min, 0.0));
+
+			gtk_adjustment_set_upper (self->priv->crop_p1_adj, MIN (self->priv->crop_p1_plus_p2 - crop_p_min, 1.0));
+			gtk_adjustment_set_upper (self->priv->crop_p2_adj, MIN (self->priv->crop_p1_plus_p2 - crop_p_min, 1.0));
 
 			gtk_adjustment_set_value (self->priv->crop_p1_adj, crop_p1);
 		}
@@ -111,8 +116,11 @@ update_crop_parameters (GthFileToolRotate *self)
 			gtk_widget_set_sensitive (GET_WIDGET ("crop_p2_label"), TRUE);
 			gtk_widget_set_sensitive (GET_WIDGET ("crop_p2_hbox"), TRUE);
 
-			gtk_adjustment_set_lower (self->priv->crop_p1_adj, 0);
-			gtk_adjustment_set_lower (self->priv->crop_p2_adj, 0);
+			gtk_adjustment_set_lower (self->priv->crop_p1_adj, 0.0);
+			gtk_adjustment_set_lower (self->priv->crop_p2_adj, 0.0);
+
+			gtk_adjustment_set_upper (self->priv->crop_p1_adj, 1.0);
+			gtk_adjustment_set_upper (self->priv->crop_p2_adj, 1.0);
 		}
 
 		gth_image_viewer_set_tool (GTH_IMAGE_VIEWER (viewer), (GthImageViewerTool *) self->priv->selector_crop);