GPencil: Fill tool refactor and Multiframe in Draw mode

This commit is a refactor of the fill tool to solve several problems we had since the first version of the tool.

Changes:

* The filling speed has been improved for each step of the process with the optimization of each algorithm/function.
* New `AutoFit` option to fill areas outside of the viewport. When enable, the total size of the frame is calculated to fit the filling area.
* New support multiframe filling. Now it is possible to fill multiple similar frames in one go.
* New `Stroke Extension` option to create temporary closing strokes. These strokes can be displayed and adjusted dynamically using wheel mouse or PageUp/Down keys.
* Parameter `Resolution` now is named `Precision` and has been moved to topbar.
* `Resolution` now has decimals and can be lower than 1 to allow quick filling in storyboarding workflows. Maximum value has been set as 5.
* Parameter `Simplify` has been moved to Advanced panel.
* Improved fill outline detection. In some cases, the outline penetrated the area to be filled with unexpected results.
* Fixes some corner case bugs with infinite loops.

As a result of this refactor, also these new functionalities has been added.

* New support for multiframe in `Draw` mode. Any drawing in active frame is duplicated to all selected frame.
* New multiframe display mode. Keyframes before or after of the active frame are displayed using onion colors. This can be disable using Onion overlay options.

1 files changed, 25 insertions, 1 deletions

diff --git a/source/blender/makesrna/intern/rna_brush.c b/source/blender/makesrna/intern/rna_brush.c
index 756841dd283..6e2e986ebf8 100644
--- a/source/blender/makesrna/intern/rna_brush.c
+++ b/source/blender/makesrna/intern/rna_brush.c
@@ -1466,7 +1466,7 @@ static void rna_def_gpencil_options(BlenderRNA *brna)
   /* fill factor size */
   prop = RNA_def_property(srna, "fill_factor", PROP_FLOAT, PROP_NONE);
   RNA_def_property_float_sdna(prop, NULL, "fill_factor");
-  RNA_def_property_range(prop, GPENCIL_MIN_FILL_FAC, 8.0f);
+  RNA_def_property_range(prop, GPENCIL_MIN_FILL_FAC, GPENCIL_MAX_FILL_FAC);
   RNA_def_property_ui_text(
       prop,
       "Precision",
@@ -1608,6 +1608,15 @@ static void rna_def_gpencil_options(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Value", "Random factor to modify original value");
   RNA_def_parameter_clear_flags(prop, PROP_ANIMATABLE, 0);
 
+  /* Factor to extend stroke extremes in Fill tool. */
+  prop = RNA_def_property(srna, "extend_stroke_factor", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fill_extend_fac");
+  RNA_def_property_range(prop, 0.0f, 10.0f);
+  RNA_def_property_float_default(prop, 0.0f);
+  RNA_def_property_ui_text(
+      prop, "Stroke Extension", "Strokes end extension for closing gaps, use zero to disable");
+  RNA_def_parameter_clear_flags(prop, PROP_ANIMATABLE, 0);
+
   /* Flags */
   prop = RNA_def_property(srna, "use_pressure", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_BRUSH_USE_PRESSURE);
@@ -1827,6 +1836,12 @@ static void rna_def_gpencil_options(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Show Lines", "Show help lines for filling to see boundaries");
   RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
 
+  prop = RNA_def_property(srna, "show_fill_extend", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_BRUSH_FILL_SHOW_EXTENDLINES);
+  RNA_def_property_boolean_default(prop, true);
+  RNA_def_property_ui_text(prop, "Show Extend Lines", "Show help lines for stroke extension");
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+
   prop = RNA_def_property(srna, "show_fill", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_negative_sdna(prop, NULL, "flag", GP_BRUSH_FILL_HIDE);
   RNA_def_property_boolean_default(prop, true);
@@ -1834,6 +1849,15 @@ static void rna_def_gpencil_options(BlenderRNA *brna)
       prop, "Show Fill", "Show transparent lines to use as boundary for filling");
   RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
 
+  prop = RNA_def_property(srna, "use_fill_autofit", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_negative_sdna(prop, NULL, "flag", GP_BRUSH_FILL_FIT_DISABLE);
+  RNA_def_property_boolean_default(prop, true);
+  RNA_def_property_ui_text(
+      prop,
+      "Automatic Fit",
+      "Fit the shape of the stroke to try to fill areas outside visible viewport");
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+
   prop = RNA_def_property(srna, "use_default_eraser", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_BRUSH_DEFAULT_ERASER);
   RNA_def_property_boolean_default(prop, true);