UV Editor: support snapping to center of pixels, in addition to corners.

Differential Revision: https://developer.blender.org/D4150

4 files changed, 40 insertions, 10 deletions

diff --git a/release/scripts/startup/bl_ui/space_image.py b/release/scripts/startup/bl_ui/space_image.py
index f3f49d82714..f163e254a48 100644
--- a/release/scripts/startup/bl_ui/space_image.py
+++ b/release/scripts/startup/bl_ui/space_image.py
@@ -353,7 +353,7 @@ class IMAGE_MT_uvs(Menu):
         uv = sima.uv_editor
         tool_settings = context.tool_settings
 
-        layout.prop(uv, "use_snap_to_pixels")
+        layout.prop_menu_enum(uv, "pixel_snap_mode")
         layout.prop(uv, "lock_bounds")
 
         layout.separator()
diff --git a/source/blender/editors/transform/transform_conversions.c b/source/blender/editors/transform/transform_conversions.c
index ce41aa85da1..5b07c0c2b49 100644
--- a/source/blender/editors/transform/transform_conversions.c
+++ b/source/blender/editors/transform/transform_conversions.c
@@ -3326,7 +3326,8 @@ finally:
 void flushTransUVs(TransInfo *t)
 {
 	SpaceImage *sima = t->sa->spacedata.first;
-	const bool use_pixel_snap = ((sima->flag & SI_PIXELSNAP) && (t->state != TRANS_CANCEL));
+	const bool use_pixel_snap = ((sima->pixel_snap_mode != SI_PIXEL_SNAP_DISABLED) &&
+	                             (t->state != TRANS_CANCEL));
 
 	FOREACH_TRANS_DATA_CONTAINER (t, tc) {
 		TransData2D *td;
@@ -3349,8 +3350,22 @@ void flushTransUVs(TransInfo *t)
 			td->loc2d[1] = td->loc[1] * aspect_inv[1];
 
 			if (use_pixel_snap) {
-				td->loc2d[0] = roundf(td->loc2d[0] * size[0]) / size[0];
-				td->loc2d[1] = roundf(td->loc2d[1] * size[1]) / size[1];
+				td->loc2d[0] *= size[0];
+				td->loc2d[1] *= size[1];
+
+				switch(sima->pixel_snap_mode) {
+					case SI_PIXEL_SNAP_CENTER:
+						td->loc2d[0] = roundf(td->loc2d[0] - 0.5f) + 0.5f;
+						td->loc2d[1] = roundf(td->loc2d[1] - 0.5f) + 0.5f;
+						break;
+					case SI_PIXEL_SNAP_CORNER:
+						td->loc2d[0] = roundf(td->loc2d[0]);
+						td->loc2d[1] = roundf(td->loc2d[1]);
+						break;
+				}
+
+				td->loc2d[0] /= size[0];
+				td->loc2d[1] /= size[1];
 			}
 		}
 	}
diff --git a/source/blender/makesdna/DNA_space_types.h b/source/blender/makesdna/DNA_space_types.h
index 4ffd6c4842e..999e160e03a 100644
--- a/source/blender/makesdna/DNA_space_types.h
+++ b/source/blender/makesdna/DNA_space_types.h
@@ -1020,10 +1020,11 @@ typedef struct SpaceImage {
 	char dt_uvstretch;
 	char around;
 
-	int pad2;
-
 	int flag;
 
+	char pixel_snap_mode;
+	char pad[3];
+
 	MaskSpaceInfo mask_info;
 } SpaceImage;
 
@@ -1042,6 +1043,13 @@ typedef enum eSpaceImage_UVDT_Stretch {
 	SI_UVDT_STRETCH_AREA = 1,
 } eSpaceImage_UVDT_Stretch;
 
+/* SpaceImage.pixel_snap_mode */
+typedef enum eSpaceImage_PixelSnapMode {
+	SI_PIXEL_SNAP_DISABLED = 0,
+	SI_PIXEL_SNAP_CENTER = 1,
+	SI_PIXEL_SNAP_CORNER = 2,
+} eSpaceImage_Snap_Mode;
+
 /* SpaceImage.mode */
 typedef enum eSpaceImage_Mode {
 	SI_MODE_VIEW  = 0,
@@ -1071,7 +1079,7 @@ typedef enum eSpaceImage_Flag {
 	SI_FLAG_DEPRECATED_7  = (1 << 7),  /* cleared */
 	SI_FLAG_DEPRECATED_8  = (1 << 8),  /* cleared */
 	SI_COORDFLOATS        = (1 << 9),
-	SI_PIXELSNAP          = (1 << 10),
+	SI_FLAG_DEPRECATED_10 = (1 << 10),
 	SI_LIVE_UNWRAP        = (1 << 11),
 	SI_USE_ALPHA          = (1 << 12),
 	SI_SHOW_ALPHA         = (1 << 13),
diff --git a/source/blender/makesrna/intern/rna_space.c b/source/blender/makesrna/intern/rna_space.c
index 66729b53394..640929ead19 100644
--- a/source/blender/makesrna/intern/rna_space.c
+++ b/source/blender/makesrna/intern/rna_space.c
@@ -2194,6 +2194,13 @@ static void rna_def_space_image_uv(BlenderRNA *brna)
 		{0, NULL, 0, NULL, NULL}
 	};
 
+		static const EnumPropertyItem pixel_snap_mode_items[] = {
+		{SI_PIXEL_SNAP_DISABLED, "DISABLED", 0, "Disabled", "Don't snap to pixels"},
+		{SI_PIXEL_SNAP_CORNER, "CORNER", 0, "Corner", "Snap to pixel corners"},
+		{SI_PIXEL_SNAP_CENTER, "CENTER", 0, "Center", "Snap to pixel centers"},
+		{0, NULL, 0, NULL, NULL}
+	};
+
 	srna = RNA_def_struct(brna, "SpaceUVEditor", NULL);
 	RNA_def_struct_sdna(srna, "SpaceImage");
 	RNA_def_struct_nested(brna, srna, "SpaceImageEditor");
@@ -2265,9 +2272,9 @@ static void rna_def_space_image_uv(BlenderRNA *brna)
 
 	/* todo: move edge and face drawing options here from G.f */
 
-	prop = RNA_def_property(srna, "use_snap_to_pixels", PROP_BOOLEAN, PROP_NONE);
-	RNA_def_property_boolean_sdna(prop, NULL, "flag", SI_PIXELSNAP);
-	RNA_def_property_ui_text(prop, "Snap to Pixels", "Snap UVs to pixel locations while editing");
+	prop = RNA_def_property(srna, "pixel_snap_mode", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_items(prop, pixel_snap_mode_items);
+	RNA_def_property_ui_text(prop, "Snap to Pixels", "Snap UVs to pixels while editing");
 	RNA_def_property_update(prop, NC_SPACE | ND_SPACE_IMAGE, NULL);
 
 	prop = RNA_def_property(srna, "lock_bounds", PROP_BOOLEAN, PROP_NONE);