Grease Pencil Todos: "Sketching Sessions"

Due to popular request and usability considerations, this commit
reintroduces functionality similar to 2.4's "Draw Mode" for Grease
Pencil.

In the toolbar under the Draw/Line/Eraser buttons, you can find the
"Use Sketching Sessions" toggle, which enables this feature. This is a
per-scene setting, and defaults to off, so that the current 2.5
behaviour is still the default (i.e. the Grease Pencil operator will
only do a single stroke at a time).

With this option enabled, drawing with Grease Pencil will enter a
semi-modal state where you can draw multiple strokes without needing
to keep holding the DKEY throughout (though you'll still need to do so
to start the strokes, unless you use some toolbar buttons), while
still being able to manipulate the viewport. Header help-text prints
show the appropriate keybindings (i.e. press ESCKEY or ENTER to end
the sketching session).

Notes:
- To aid maintainability of the 3D-View toolbar code, I've taken the
liberty to factor out the groups of widgets which commonly occur in
most of the toolbars into separate functions (namely "Repeat" and
"Grease Pencil"). Perhaps it might make it slightly harder to newbies
to the toolbar code to grasp, though the physics panels are far worse
;)
- I've reshuffled some code in the Grease Pencil code to separate out
the various states of operation again more clearly, though some more
work is still needed there (TODO)
- There can now be only one Grease Pencil operator running at a time
- Redoing Grease Pencil operations where sketching sessions was
enabled still needs work. Namely, a way of delimiting the set of
points recorded into strokes is still needed (TODO)
- Ultimately, it should be possible to switch tools midway through a
session. Currently sessions are limited to only being able to be used
with a single drawing mode (TODO)
- After ending a drawing session, the titlebar contols may not work on
Windows without manually making the main window lose focus and then
regain (i.e. click on some other window in toolbar, then come back).
This may be related to (bug #25480)

1 files changed, 8 insertions, 2 deletions

diff --git a/source/blender/makesdna/DNA_scene_types.h b/source/blender/makesdna/DNA_scene_types.h
index 1b597f45884..de589f27abc 100644
--- a/source/blender/makesdna/DNA_scene_types.h
+++ b/source/blender/makesdna/DNA_scene_types.h
@@ -657,8 +657,11 @@ typedef struct ToolSettings {
 	short uvcalc_mapalign;
 	short uvcalc_flag;
 	short uv_flag, uv_selectmode;
-	short uv_pad[2];
-
+	short uv_pad;
+	
+	/* Grease Pencil */
+	short gpencil_flags;
+	
 	/* Auto-IK */
 	short autoik_chainlen;
 
@@ -1193,6 +1196,9 @@ typedef enum SculptFlags {
 #define EDGE_MODE_TAG_CREASE			3
 #define EDGE_MODE_TAG_BEVEL				4
 
+/* toolsettings->gpencil_flags */
+#define GP_TOOL_FLAG_PAINTSESSIONS_ON	(1<<0)
+
 /* toolsettings->particle flag */
 #define PE_KEEP_LENGTHS			1
 #define PE_LOCK_FIRST			2