Grease Pencil - Storyboarding Features (merge from GPencil_EditStrokes branch)

This merge-commit brings in a number of new features and workflow/UI improvements for
working with Grease Pencil. While these were originally targetted at improving
the workflow for creating 3D storyboards in Blender using the Grease Pencil,
many of these changes should also prove useful in other workflows too.

The main highlights here are:
1) It is now possible to edit Grease Pencil strokes
   - Use D Tab, or toggle the "Enable Editing" toggles in the Toolbar/Properties regions
     to enter "Stroke Edit Mode". In this mode, many common editing tools will
     operate on Grease Pencil stroke points instead.
   - Tools implemented include Select, Select All/Border/Circle/Linked/More/Less,
     Grab, Rotate, Scale, Bend, Shear, To Sphere, Mirror, Duplicate, Delete.
   - Proportional Editing works when using the transform tools

2) Grease Pencil stroke settings can now be animated
   NOTE: Currently drivers don't work, but if time allows, this may still be
         added before the release.

3) Strokes can be drawn with "filled" interiors, using a separate set of
   colour/opacity settings to the ones used for the lines themselves.

   This makes use of OpenGL filled polys, which has the limitation of only
   being able to fill convex shapes. Some artifacts may be visible on concave
   shapes (e.g. pacman's mouth will be overdrawn)

4) "Volumetric Strokes" - An alternative drawing technique for stroke drawing
   has been added which draws strokes as a series of screen-aligned discs.

   While this was originally a partial experimental technique at getting better
   quality 3D lines, the effects possible using this technique were interesting
   enough to warrant making this a dedicated feature. Best results when partial
   opacity and large stroke widths are used.

5) Improved Onion Skinning Support
   - Different colours can be selected for the before/after ghosts. To do so,
     enable the "colour wheel" toggle beside the Onion Skinning toggle, and set
     the colours accordingly.
   - Different numbers of ghosts can be shown before/after the current frame

6) Grease Pencil datablocks are now attached to the scene by default instead of
   the active object.
   - For a long time, the object-attachment has proved to be quite problematic
     for users to keep track of. Now that this is done at scene level, it is
     easier for most users to use.
   - An exception for old files (and for any addons which may benefit from object
     attachment instead), is that if the active object has a Grease Pencil datablock,
     that will be used instead.
   - It is not currently possible to choose object-attachment from the UI, but
     it is simple to do this from the console instead, by doing:
     context.active_object.grease_pencil = bpy.data.grease_pencil["blah"]

7) Various UI Cleanups
   - The layers UI has been cleaned up to use a list instead of the nested-panels
     design. Apart from saving space, this is also much nicer to look at now.

   - The UI code is now all defined in Python. To support this, it has been necessary
     to add some new context properties to make it easier to access these settings.
     e.g. "gpencil_data" for the datablock
          "active_gpencil_layer" and "active_gpencil_frame" for active data,
          "editable_gpencil_strokes" for the strokes that can be edited

   - The "stroke placement/alignment" settings (previously "Drawing Settings" at the
     bottom of the Grease Pencil panel in the Properties Region) is now located in
     the toolbar. These were more toolsettings than properties for how GPencil got drawn.

   - "Use Sketching Sessions" has been renamed "Continuous Drawing", as per a
     suggestion for an earlier discussion on developer.blender.org

   - By default, the painting operator will wait for a mouse button to be pressed
     before it starts creating the stroke. This is to make it easier to include
     this operator in various toolbars/menus/etc.   To get it immediately starting
     (as when you hold down DKEy to draw), set "wait_for_input" to False.

   - GPencil Layers can be rearranged in the "Grease Pencil" mode of the Action Editor

   - Toolbar panels have been added to all the other editors which support these.

8) Pie menus for quick-access to tools
   A set of experimental pie menus has been included for quick access to many
   tools and settings. It is not necessary to use these to get things done,
   but they have been designed to help make certain common tasks easier.

   - Ctrl-D = The main pie menu. Reveals tools in a context sensitive and
              spatially stable manner.
   - D Q    = "Quick Settings" pie. This allows quick access to the active
              layer's settings. Notably, colours, thickness, and turning
              onion skinning on/off.

1 files changed, 166 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
new file mode 100644
index 00000000000..4a913c3d2e5
--- /dev/null
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -0,0 +1,166 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2014, Blender Foundation
+ *
+ * Contributor(s): Joshua Leung
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/editors/gpencil/gpencil_utils.c
+ *  \ingroup edgpencil
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <math.h>
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_math.h"
+#include "BLI_blenlib.h"
+#include "BLI_utildefines.h"
+
+#include "DNA_gpencil_types.h"
+#include "DNA_object_types.h"
+#include "DNA_scene_types.h"
+#include "DNA_screen_types.h"
+#include "DNA_space_types.h"
+#include "DNA_view3d_types.h"
+
+#include "BKE_context.h"
+#include "BKE_global.h"
+#include "BKE_gpencil.h"
+#include "BKE_library.h"
+#include "BKE_object.h"
+#include "BKE_report.h"
+#include "BKE_scene.h"
+#include "BKE_screen.h"
+
+#include "UI_interface.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "RNA_access.h"
+#include "RNA_define.h"
+
+#include "UI_view2d.h"
+
+#include "ED_gpencil.h"
+#include "ED_view3d.h"
+
+#include "gpencil_intern.h"
+
+/* ******************************************************** */
+
+/* Check if part of stroke occurs within last segment drawn by eraser */
+bool gp_stroke_inside_circle(const int mval[2], const int UNUSED(mvalo[2]),
+                             int rad, int x0, int y0, int x1, int y1)
+{
+	/* simple within-radius check for now */
+	const float mval_fl[2]     = {mval[0], mval[1]};
+	const float screen_co_a[2] = {x0, y0};
+	const float screen_co_b[2] = {x1, y1};
+	
+	if (edge_inside_circle(mval_fl, rad, screen_co_a, screen_co_b)) {
+		return true;
+	}
+	
+	/* not inside */
+	return false;
+}
+
+/* ******************************************************** */
+
+/* Init handling for space-conversion function (from passed-in parameters) */
+void gp_point_conversion_init(bContext *C, GP_SpaceConversion *r_gsc)
+{
+	ScrArea *sa = CTX_wm_area(C);
+	ARegion *ar = CTX_wm_region(C);
+	
+	/* zero out the storage (just in case) */
+	memset(r_gsc, 0, sizeof(GP_SpaceConversion));
+	unit_m4(r_gsc->mat);
+	
+	/* store settings */
+	r_gsc->sa = sa;
+	r_gsc->ar = ar;
+	r_gsc->v2d = &ar->v2d;
+	
+	/* init region-specific stuff */
+	if (sa->spacetype == SPACE_VIEW3D) {
+		wmWindow *win = CTX_wm_window(C);
+		Scene *scene = CTX_data_scene(C);
+		View3D *v3d = (View3D *)CTX_wm_space_data(C);
+		RegionView3D *rv3d = ar->regiondata;
+		
+		/* init 3d depth buffers */
+		view3d_operator_needs_opengl(C);
+		
+		view3d_region_operator_needs_opengl(win, ar);
+		ED_view3d_autodist_init(scene, ar, v3d, 0);
+		
+		/* for camera view set the subrect */
+		if (rv3d->persp == RV3D_CAMOB) {
+			ED_view3d_calc_camera_border(scene, ar, v3d, rv3d, &r_gsc->subrect_data, true); /* no shift */
+			r_gsc->subrect = &r_gsc->subrect_data;
+		}
+	}
+}
+
+
+/* Convert Grease Pencil points to screen-space values */
+void gp_point_to_xy(GP_SpaceConversion *gsc, bGPDstroke *gps, bGPDspoint *pt,
+                    int *r_x, int *r_y)
+{
+	ARegion *ar = gsc->ar;
+	View2D *v2d = gsc->v2d;
+	rctf *subrect = gsc->subrect;
+	int xyval[2];
+
+	if (gps->flag & GP_STROKE_3DSPACE) {
+		if (ED_view3d_project_int_global(ar, &pt->x, xyval, V3D_PROJ_TEST_NOP) == V3D_PROJ_RET_OK) {
+			*r_x = xyval[0];
+			*r_y = xyval[1];
+		}
+		else {
+			*r_x = V2D_IS_CLIPPED;
+			*r_y = V2D_IS_CLIPPED;
+		}
+	}
+	else if (gps->flag & GP_STROKE_2DSPACE) {
+		float vec[3] = {pt->x, pt->y, 0.0f};
+		mul_m4_v3(gsc->mat, vec);
+		UI_view2d_view_to_region_clip(v2d, vec[0], vec[1], r_x, r_y);
+	}
+	else {
+		if (subrect == NULL) { /* normal 3D view */
+			*r_x = (int)(pt->x / 100 * ar->winx);
+			*r_y = (int)(pt->y / 100 * ar->winy);
+		}
+		else { /* camera view, use subrect */
+			*r_x = (int)((pt->x / 100) * BLI_rctf_size_x(subrect)) + subrect->xmin;
+			*r_y = (int)((pt->y / 100) * BLI_rctf_size_y(subrect)) + subrect->ymin;
+		}
+	}
+}
+
+/* ******************************************************** */