Manipulator: ruler tool

Add the 3D view ruler as a tool,
the modal operator remains for now
however it may be removed if we use the tool-system for 2.8.

Note that this does copy code from the operator,
its different enough not to attempt to de-duplicate.

5 files changed, 1091 insertions, 1 deletions

diff --git a/source/blender/editors/space_view3d/CMakeLists.txt b/source/blender/editors/space_view3d/CMakeLists.txt
index db79d578b5d..de8380aa8bb 100644
--- a/source/blender/editors/space_view3d/CMakeLists.txt
+++ b/source/blender/editors/space_view3d/CMakeLists.txt
@@ -64,6 +64,7 @@ set(SRC
 	view3d_manipulator_empty.c
 	view3d_manipulator_forcefield.c
 	view3d_manipulator_lamp.c
+	view3d_manipulator_ruler.c
 	view3d_ops.c
 	view3d_project.c
 	view3d_ruler.c
diff --git a/source/blender/editors/space_view3d/space_view3d.c b/source/blender/editors/space_view3d/space_view3d.c
index 3e7b3f0f008..44e1d999c2a 100644
--- a/source/blender/editors/space_view3d/space_view3d.c
+++ b/source/blender/editors/space_view3d/space_view3d.c
@@ -724,6 +724,9 @@ static void view3d_widgets(void)
 	WM_manipulatorgrouptype_append_and_link(mmap_type, VIEW3D_WGT_armature_spline);
 
 	WM_manipulatorgrouptype_append(VIEW3D_WGT_xform_cage);
+
+	WM_manipulatorgrouptype_append(VIEW3D_WGT_ruler);
+	WM_manipulatortype_append(VIEW3D_WT_ruler_item);
 }
 
 
diff --git a/source/blender/editors/space_view3d/view3d_intern.h b/source/blender/editors/space_view3d/view3d_intern.h
index f37a0eeaaa2..e42a1e7f286 100644
--- a/source/blender/editors/space_view3d/view3d_intern.h
+++ b/source/blender/editors/space_view3d/view3d_intern.h
@@ -50,9 +50,10 @@ struct bPoseChannel;
 struct Mesh;
 struct SceneLayer;
 struct wmOperatorType;
-struct wmWindowManager;
 struct wmKeyConfig;
 struct wmManipulatorGroupType;
+struct wmManipulatorType;
+struct wmWindowManager;
 
 /* drawing flags: */
 enum {
@@ -338,6 +339,10 @@ void VIEW3D_WGT_force_field(struct wmManipulatorGroupType *wgt);
 void VIEW3D_WGT_empty_image(struct wmManipulatorGroupType *wgt);
 void VIEW3D_WGT_armature_spline(struct wmManipulatorGroupType *wgt);
 
+void VIEW3D_WGT_ruler(struct wmManipulatorGroupType *wgt);
+void VIEW3D_WT_ruler_item(struct wmManipulatorType *wt);
+void VIEW3D_OT_ruler_add(struct wmOperatorType *ot);
+
 /* draw_volume.c */
 void draw_smoke_volume(struct SmokeDomainSettings *sds, struct Object *ob,
                        const float min[3], const float max[3],
diff --git a/source/blender/editors/space_view3d/view3d_manipulator_ruler.c b/source/blender/editors/space_view3d/view3d_manipulator_ruler.c
new file mode 100644
index 00000000000..01cf67259a4
--- /dev/null
+++ b/source/blender/editors/space_view3d/view3d_manipulator_ruler.c
@@ -0,0 +1,1079 @@
+/*
+ * ***** 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.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/editors/space_view3d/view3d_manipulator_ruler.c
+ *  \ingroup spview3d
+ */
+
+#include "BLI_listbase.h"
+#include "BLI_string.h"
+#include "BLI_rect.h"
+#include "BLI_math.h"
+#include "BLI_utildefines.h"
+
+#include "BLT_translation.h"
+
+#include "BKE_context.h"
+#include "BKE_object.h"
+#include "BKE_gpencil.h"
+#include "BKE_unit.h"
+
+#include "DNA_object_types.h"
+#include "DNA_gpencil_types.h"
+#include "DNA_view3d_types.h"
+
+#include "BIF_gl.h"
+
+#include "ED_screen.h"
+#include "ED_transform_snap_object_context.h"
+#include "ED_view3d.h"
+
+#include "UI_resources.h"
+#include "UI_interface.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "RNA_access.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "view3d_intern.h"  /* own include */
+
+#include "GPU_immediate.h"
+#include "GPU_immediate_util.h"
+#include "GPU_select.h"
+
+#include "BLF_api.h"
+
+
+static const char *view3d_wgt_ruler_id = "VIEW3D_WGT_ruler";
+
+
+#define MVAL_MAX_PX_DIST 12.0f
+
+/* -------------------------------------------------------------------- */
+/* Ruler Item (we can have many) */
+enum {
+	RULERITEM_USE_ANGLE = (1 << 0),  /* use protractor */
+	RULERITEM_USE_RAYCAST = (1 << 1)
+};
+
+enum {
+	RULERITEM_DIRECTION_IN = 0,
+	RULERITEM_DIRECTION_OUT
+};
+
+/* keep smaller then selection, since we may want click elsewhere without selecting a ruler */
+#define RULER_PICK_DIST 12.0f
+#define RULER_PICK_DIST_SQ (RULER_PICK_DIST * RULER_PICK_DIST)
+
+/* not clicking on a point */
+#define PART_LINE 0xff
+
+/* -------------------------------------------------------------------- */
+/* Ruler Info (wmManipulatorGroup customdata) */
+
+enum {
+	RULER_STATE_NORMAL = 0,
+	RULER_STATE_DRAG
+};
+
+enum {
+	RULER_SNAP_OK = (1 << 0),
+};
+
+typedef struct RulerInfo {
+	// ListBase items;
+	int      item_active;
+	int flag;
+	int snap_flag;
+	int state;
+
+	struct SnapObjectContext *snap_context;
+
+	/* wm state */
+	wmWindow *win;
+	ScrArea *sa;
+	ARegion *ar;  /* re-assigned every modal update */
+} RulerInfo;
+
+/* -------------------------------------------------------------------- */
+/* Ruler Item (two or three points) */
+
+typedef struct RulerItem {
+	wmManipulator mpr;
+
+	/* worldspace coords, middle being optional */
+	float co[3][3];
+
+	int   flag;
+	int   raycast_dir;  /* RULER_DIRECTION_* */
+} RulerItem;
+
+typedef struct RulerInteraction {
+	/* selected coord */
+	char  co_index; /* 0 -> 2 */
+	float drag_start_co[3];
+	uint inside_region : 1;
+} RulerInteraction;
+
+/* -------------------------------------------------------------------- */
+/** \name Internal Ruler Utilities
+ * \{ */
+
+static RulerItem *ruler_item_add(wmManipulatorGroup *mgroup)
+{
+	/* could pass this as an arg */
+	const wmManipulatorType *wt_ruler = WM_manipulatortype_find("VIEW3D_WT_ruler_item", true);
+	RulerItem *ruler_item = (RulerItem *)WM_manipulator_new_ptr(wt_ruler, mgroup, NULL);
+	WM_manipulator_set_flag(&ruler_item->mpr, WM_MANIPULATOR_DRAW_MODAL, true);
+	return ruler_item;
+}
+
+static void ruler_item_as_string(RulerItem *ruler_item, UnitSettings *unit,
+                                 char *numstr, size_t numstr_size, int prec)
+{
+	const bool do_split = (unit->flag & USER_UNIT_OPT_SPLIT) != 0;
+
+	if (ruler_item->flag & RULERITEM_USE_ANGLE) {
+		const float ruler_angle = angle_v3v3v3(ruler_item->co[0],
+		                                       ruler_item->co[1],
+		                                       ruler_item->co[2]);
+
+		if (unit->system == USER_UNIT_NONE) {
+			BLI_snprintf(numstr, numstr_size, "%.*f°", prec, RAD2DEGF(ruler_angle));
+		}
+		else {
+			bUnit_AsString(numstr, numstr_size,
+			               (double)ruler_angle,
+			               prec, unit->system, B_UNIT_ROTATION, do_split, false);
+		}
+	}
+	else {
+		const float ruler_len = len_v3v3(ruler_item->co[0],
+		                                 ruler_item->co[2]);
+
+		if (unit->system == USER_UNIT_NONE) {
+			BLI_snprintf(numstr, numstr_size, "%.*f", prec, ruler_len);
+		}
+		else {
+			bUnit_AsString(numstr, numstr_size,
+			               (double)(ruler_len * unit->scale_length),
+			               prec, unit->system, B_UNIT_LENGTH, do_split, false);
+		}
+	}
+}
+
+static bool view3d_ruler_pick(
+        wmManipulatorGroup *mgroup, RulerItem *ruler_item, const float mval[2],
+        int *r_co_index)
+{
+	RulerInfo *ruler_info = mgroup->customdata;
+	ARegion *ar = ruler_info->ar;
+	bool found = false;
+
+	float dist_best = RULER_PICK_DIST_SQ;
+	int co_index_best = -1;
+
+	{
+		float co_ss[3][2];
+		float dist;
+		int j;
+
+		/* should these be checked? - ok for now not to */
+		for (j = 0; j < 3; j++) {
+			ED_view3d_project_float_global(ar, ruler_item->co[j], co_ss[j], V3D_PROJ_TEST_NOP);
+		}
+
+		if (ruler_item->flag & RULERITEM_USE_ANGLE) {
+			dist = min_ff(dist_squared_to_line_segment_v2(mval, co_ss[0], co_ss[1]),
+			              dist_squared_to_line_segment_v2(mval, co_ss[1], co_ss[2]));
+			if (dist < dist_best) {
+				dist_best = dist;
+				found = true;
+
+				{
+					const float dist_points[3] = {
+					    len_squared_v2v2(co_ss[0], mval),
+					    len_squared_v2v2(co_ss[1], mval),
+					    len_squared_v2v2(co_ss[2], mval),
+					};
+					if (min_fff(UNPACK3(dist_points)) < RULER_PICK_DIST_SQ) {
+						co_index_best = min_axis_v3(dist_points);
+					}
+					else {
+						co_index_best = -1;
+					}
+				}
+			}
+		}
+		else {
+			dist = dist_squared_to_line_segment_v2(mval, co_ss[0], co_ss[2]);
+			if (dist < dist_best) {
+				dist_best = dist;
+				found = true;
+
+				{
+					const float dist_points[2] = {
+					    len_squared_v2v2(co_ss[0], mval),
+					    len_squared_v2v2(co_ss[2], mval),
+					};
+					if (min_ff(UNPACK2(dist_points)) < RULER_PICK_DIST_SQ) {
+						co_index_best = (dist_points[0] < dist_points[1]) ? 0 : 2;
+					}
+					else {
+						co_index_best = -1;
+					}
+				}
+			}
+		}
+	}
+
+	*r_co_index = co_index_best;
+	return found;
+}
+
+/**
+ * Ensure the 'snap_context' is only cached while dragging,
+ * needed since the user may toggle modes between tool use.
+ */
+static void ruler_state_set(bContext *C, RulerInfo *ruler_info, int state)
+{
+	if (state == ruler_info->state) {
+		return;
+	}
+
+	/* always remove */
+	if (ruler_info->snap_context) {
+		ED_transform_snap_object_context_destroy(ruler_info->snap_context);
+		ruler_info->snap_context = NULL;
+	}
+
+	if (state == RULER_STATE_NORMAL) {
+		/* pass */
+	}
+	else if (state == RULER_STATE_DRAG) {
+		ruler_info->snap_context = ED_transform_snap_object_context_create_view3d(
+		        CTX_data_main(C), CTX_data_scene(C), CTX_data_scene_layer(C), CTX_data_engine(C), 0,
+		        ruler_info->ar, CTX_wm_view3d(C));
+	}
+	else {
+		BLI_assert(0);
+	}
+
+	ruler_info->state = state;
+}
+
+static void view3d_ruler_item_project(
+        RulerInfo *ruler_info, float r_co[3],
+        const int xy[2])
+{
+	ED_view3d_win_to_3d_int(ruler_info->sa->spacedata.first, ruler_info->ar, r_co, xy, r_co);
+}
+
+/* use for mousemove events */
+static bool view3d_ruler_item_mousemove(
+        RulerInfo *ruler_info, RulerItem *ruler_item, const int mval[2],
+        const bool do_thickness, const bool do_snap)
+{
+	RulerInteraction *inter = ruler_item->mpr.interaction_data;
+	const float eps_bias = 0.0002f;
+	float dist_px = MVAL_MAX_PX_DIST * U.pixelsize;  /* snap dist */
+
+	ruler_info->snap_flag &= ~RULER_SNAP_OK;
+
+	if (ruler_item) {
+		float *co = ruler_item->co[inter->co_index];
+		/* restore the initial depth */
+		copy_v3_v3(co, inter->drag_start_co);
+		view3d_ruler_item_project(ruler_info, co, mval);
+		if (do_thickness && inter->co_index != 1) {
+			// Scene *scene = CTX_data_scene(C);
+			// View3D *v3d = ruler_info->sa->spacedata.first;
+			const float mval_fl[2] = {UNPACK2(mval)};
+			float ray_normal[3];
+			float ray_start[3];
+			float *co_other;
+
+			co_other = ruler_item->co[inter->co_index == 0 ? 2 : 0];
+
+			if (ED_transform_snap_object_project_view3d_mixed(
+			        ruler_info->snap_context,
+			        SCE_SELECT_FACE,
+			        &(const struct SnapObjectParams){
+			            .snap_select = SNAP_ALL,
+			            .use_object_edit_cage = true,
+			        },
+			        mval_fl, &dist_px, true,
+			        co, ray_normal))
+			{
+				negate_v3(ray_normal);
+				/* add some bias */
+				madd_v3_v3v3fl(ray_start, co, ray_normal, eps_bias);
+				ED_transform_snap_object_project_ray(
+				        ruler_info->snap_context,
+				        &(const struct SnapObjectParams){
+				            .snap_select = SNAP_ALL,
+				            .use_object_edit_cage = true,
+				        },
+				        ray_start, ray_normal, NULL,
+				        co_other, NULL);
+			}
+		}
+		else if (do_snap) {
+			// Scene *scene = CTX_data_scene(C);
+			View3D *v3d = ruler_info->sa->spacedata.first;
+			const float mval_fl[2] = {UNPACK2(mval)};
+			bool use_depth = (v3d->drawtype >= OB_SOLID);
+
+			if (ED_transform_snap_object_project_view3d_mixed(
+			        ruler_info->snap_context,
+			        (SCE_SELECT_VERTEX | SCE_SELECT_EDGE) | (use_depth ? SCE_SELECT_FACE : 0),
+			        &(const struct SnapObjectParams){
+			            .snap_select = SNAP_ALL,
+			            .use_object_edit_cage = true,
+			        },
+			        mval_fl, &dist_px, use_depth,
+			        co, NULL))
+			{
+				ruler_info->snap_flag |= RULER_SNAP_OK;
+			}
+		}
+		return true;
+	}
+	else {
+		return false;
+	}
+}
+
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Ruler/Grease Pencil Conversion
+ * \{ */
+
+#define RULER_ID "RulerData3D"
+static bool view3d_ruler_to_gpencil(bContext *C, wmManipulatorGroup *mgroup)
+{
+	// RulerInfo *ruler_info = mgroup->customdata;
+	Scene *scene = CTX_data_scene(C);
+	bGPDlayer *gpl;
+	bGPDframe *gpf;
+	bGPDstroke *gps;
+	bGPDpalette *palette;
+	bGPDpalettecolor *palcolor;
+	RulerItem *ruler_item;
+	const char *ruler_name = RULER_ID;
+	bool changed = false;
+
+	if (scene->gpd == NULL) {
+		scene->gpd = BKE_gpencil_data_addnew("GPencil");
+	}
+
+	gpl = BLI_findstring(&scene->gpd->layers, ruler_name, offsetof(bGPDlayer, info));
+	if (gpl == NULL) {
+		gpl = BKE_gpencil_layer_addnew(scene->gpd, ruler_name, false);
+		gpl->thickness = 1;
+		gpl->flag |= GP_LAYER_HIDE;
+	}
+
+	/* try to get active palette or create a new one */
+	palette = BKE_gpencil_palette_getactive(scene->gpd);
+	if (palette == NULL) {
+		palette = BKE_gpencil_palette_addnew(scene->gpd, DATA_("GP_Palette"), true);
+	}
+	/* try to get color with the ruler name or create a new one */
+	palcolor = BKE_gpencil_palettecolor_getbyname(palette, (char *)ruler_name);
+	if (palcolor == NULL) {
+		palcolor = BKE_gpencil_palettecolor_addnew(palette, (char *)ruler_name, true);
+	}
+
+	gpf = BKE_gpencil_layer_getframe(gpl, CFRA, true);
+	BKE_gpencil_free_strokes(gpf);
+
+	for (ruler_item = mgroup->manipulators.first; ruler_item; ruler_item = (RulerItem *)ruler_item->mpr.next) {
+		bGPDspoint *pt;
+		int j;
+
+		/* allocate memory for a new stroke */
+		gps = MEM_callocN(sizeof(bGPDstroke), "gp_stroke");
+		if (ruler_item->flag & RULERITEM_USE_ANGLE) {
+			gps->totpoints = 3;
+			pt = gps->points = MEM_callocN(sizeof(bGPDspoint) * gps->totpoints, "gp_stroke_points");
+			for (j = 0; j < 3; j++) {
+				copy_v3_v3(&pt->x, ruler_item->co[j]);
+				pt->pressure = 1.0f;
+				pt->strength = 1.0f;
+				pt++;
+			}
+		}
+		else {
+			gps->totpoints = 2;
+			pt = gps->points = MEM_callocN(sizeof(bGPDspoint) * gps->totpoints, "gp_stroke_points");
+			for (j = 0; j < 3; j += 2) {
+				copy_v3_v3(&pt->x, ruler_item->co[j]);
+				pt->pressure = 1.0f;
+				pt->strength = 1.0f;
+				pt++;
+			}
+		}
+		gps->flag = GP_STROKE_3DSPACE;
+		gps->thickness = 3;
+		/* assign color to stroke */
+		BLI_strncpy(gps->colorname, palcolor->info, sizeof(gps->colorname));
+		gps->palcolor = palcolor;
+		BLI_addtail(&gpf->strokes, gps);
+		changed = true;
+	}
+
+	return changed;
+}
+
+static bool view3d_ruler_from_gpencil(const bContext *C, wmManipulatorGroup *mgroup)
+{
+	Scene *scene = CTX_data_scene(C);
+	bool changed = false;
+
+	if (scene->gpd) {
+		bGPDlayer *gpl;
+		const char *ruler_name = RULER_ID;
+		gpl = BLI_findstring(&scene->gpd->layers, ruler_name, offsetof(bGPDlayer, info));
+		if (gpl) {
+			bGPDframe *gpf;
+			gpf = BKE_gpencil_layer_getframe(gpl, CFRA, false);
+			if (gpf) {
+				bGPDstroke *gps;
+				for (gps = gpf->strokes.first; gps; gps = gps->next) {
+					bGPDspoint *pt = gps->points;
+					int j;
+					RulerItem *ruler_item = NULL;
+					if (gps->totpoints == 3) {
+						ruler_item = ruler_item_add(mgroup);
+						for (j = 0; j < 3; j++) {
+							copy_v3_v3(ruler_item->co[j], &pt->x);
+							pt++;
+						}
+						ruler_item->flag |= RULERITEM_USE_ANGLE;
+						changed = true;
+					}
+					else if (gps->totpoints == 2) {
+						ruler_item = ruler_item_add(mgroup);
+						for (j = 0; j < 3; j += 2) {
+							copy_v3_v3(ruler_item->co[j], &pt->x);
+							pt++;
+						}
+						changed = true;
+					}
+				}
+			}
+		}
+	}
+
+	return changed;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Ruler Item Manipulator Type
+ * \{ */
+
+static void manipulator_ruler_draw(const bContext *C, wmManipulator *mpr)
+{
+	Scene *scene = CTX_data_scene(C);
+	UnitSettings *unit = &scene->unit;
+	RulerInfo *ruler_info = mpr->parent_mgroup->customdata;
+	RulerItem *ruler_item = (RulerItem *)mpr;
+	ARegion *ar = ruler_info->ar;
+	RegionView3D *rv3d = ar->regiondata;
+	const float cap_size = 4.0f;
+	const float bg_margin = 4.0f * U.pixelsize;
+	const float bg_radius = 4.0f * U.pixelsize;
+	const float arc_size = 64.0f * U.pixelsize;
+#define ARC_STEPS 24
+	const int arc_steps = ARC_STEPS;
+	const float color_act[4] = {1.0f, 1.0f, 1.0f, 1.0f};
+	const float color_base[4] = {0.0f, 0.0f, 0.0f, 1.0f};
+	unsigned char color_text[3];
+	unsigned char color_wire[3];
+	float color_back[4] = {1.0f, 1.0f, 1.0f, 0.5f};
+
+	/* anti-aliased lines for more consistent appearance */
+	glEnable(GL_LINE_SMOOTH);
+
+	BLF_enable(blf_mono_font, BLF_ROTATION);
+	BLF_size(blf_mono_font, 14 * U.pixelsize, U.dpi);
+	BLF_rotation(blf_mono_font, 0.0f);
+
+	UI_GetThemeColor3ubv(TH_TEXT, color_text);
+	UI_GetThemeColor3ubv(TH_WIRE, color_wire);
+
+	const bool is_act = (mpr->flag & WM_MANIPULATOR_DRAW_HOVER);
+	float dir_ruler[2];
+	float co_ss[3][2];
+	int j;
+
+	/* should these be checked? - ok for now not to */
+	for (j = 0; j < 3; j++) {
+		ED_view3d_project_float_global(ar, ruler_item->co[j], co_ss[j], V3D_PROJ_TEST_NOP);
+	}
+
+	glEnable(GL_BLEND);
+
+	const uint shdr_pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+
+	if (ruler_item->flag & RULERITEM_USE_ANGLE) {
+		immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);
+
+		float viewport_size[4];
+		glGetFloatv(GL_VIEWPORT, viewport_size);
+		immUniform2f("viewport_size", viewport_size[2], viewport_size[3]);
+
+		immUniform1i("num_colors", 2);  /* "advanced" mode */
+		const float *col = is_act ? color_act : color_base;
+		immUniformArray4fv("colors", (float *)(float[][4]){{0.67f, 0.67f, 0.67f, 1.0f}, {col[0], col[1], col[2], col[3]}}, 2);
+		immUniform1f("dash_width", 6.0f);
+
+		immBegin(GWN_PRIM_LINE_STRIP, 3);
+
+		immVertex2fv(shdr_pos, co_ss[0]);
+		immVertex2fv(shdr_pos, co_ss[1]);
+		immVertex2fv(shdr_pos, co_ss[2]);
+
+		immEnd();
+
+		immUnbindProgram();
+
+		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+
+		/* arc */
+		{
+			float dir_tmp[3];
+			float co_tmp[3];
+			float arc_ss_coord[2];
+
+			float dir_a[3];
+			float dir_b[3];
+			float quat[4];
+			float axis[3];
+			float angle;
+			const float px_scale = (ED_view3d_pixel_size(rv3d, ruler_item->co[1]) *
+			                        min_fff(arc_size,
+			                                len_v2v2(co_ss[0], co_ss[1]) / 2.0f,
+			                                len_v2v2(co_ss[2], co_ss[1]) / 2.0f));
+
+			sub_v3_v3v3(dir_a, ruler_item->co[0], ruler_item->co[1]);
+			sub_v3_v3v3(dir_b, ruler_item->co[2], ruler_item->co[1]);
+			normalize_v3(dir_a);
+			normalize_v3(dir_b);
+
+			cross_v3_v3v3(axis, dir_a, dir_b);
+			angle = angle_normalized_v3v3(dir_a, dir_b);
+
+			axis_angle_to_quat(quat, axis, angle / arc_steps);
+
+			copy_v3_v3(dir_tmp, dir_a);
+
+			immUniformColor3ubv(color_wire);
+
+			immBegin(GWN_PRIM_LINE_STRIP, arc_steps + 1);
+
+			for (j = 0; j <= arc_steps; j++) {
+				madd_v3_v3v3fl(co_tmp, ruler_item->co[1], dir_tmp, px_scale);
+				ED_view3d_project_float_global(ar, co_tmp, arc_ss_coord, V3D_PROJ_TEST_NOP);
+				mul_qt_v3(quat, dir_tmp);
+
+				immVertex2fv(shdr_pos, arc_ss_coord);
+			}
+
+			immEnd();
+		}
+
+		/* capping */
+		{
+			float rot_90_vec_a[2];
+			float rot_90_vec_b[2];
+			float cap[2];
+
+			sub_v2_v2v2(dir_ruler, co_ss[0], co_ss[1]);
+			rot_90_vec_a[0] = -dir_ruler[1];
+			rot_90_vec_a[1] =  dir_ruler[0];
+			normalize_v2(rot_90_vec_a);
+
+			sub_v2_v2v2(dir_ruler, co_ss[1], co_ss[2]);
+			rot_90_vec_b[0] = -dir_ruler[1];
+			rot_90_vec_b[1] =  dir_ruler[0];
+			normalize_v2(rot_90_vec_b);
+
+			glEnable(GL_BLEND);
+
+			immUniformColor3ubv(color_wire);
+
+			immBegin(GWN_PRIM_LINES, 8);
+
+			madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec_a, cap_size);
+			immVertex2fv(shdr_pos, cap);
+			madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec_a, -cap_size);
+			immVertex2fv(shdr_pos, cap);
+
+			madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec_b, cap_size);
+			immVertex2fv(shdr_pos, cap);
+			madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec_b, -cap_size);
+			immVertex2fv(shdr_pos, cap);
+
+			/* angle vertex */
+			immVertex2f(shdr_pos, co_ss[1][0] - cap_size, co_ss[1][1] - cap_size);
+			immVertex2f(shdr_pos, co_ss[1][0] + cap_size, co_ss[1][1] + cap_size);
+			immVertex2f(shdr_pos, co_ss[1][0] - cap_size, co_ss[1][1] + cap_size);
+			immVertex2f(shdr_pos, co_ss[1][0] + cap_size, co_ss[1][1] - cap_size);
+
+			immEnd();
+
+			glDisable(GL_BLEND);
+		}
+
+		immUnbindProgram();
+
+		/* text */
+		{
+			char numstr[256];
+			float numstr_size[2];
+			float posit[2];
+			const int prec = 2;  /* XXX, todo, make optional */
+
+			ruler_item_as_string(ruler_item, unit, numstr, sizeof(numstr), prec);
+
+			BLF_width_and_height(blf_mono_font, numstr, sizeof(numstr), &numstr_size[0], &numstr_size[1]);
+
+			posit[0] = co_ss[1][0] + (cap_size * 2.0f);
+			posit[1] = co_ss[1][1] - (numstr_size[1] / 2.0f);
+
+			/* draw text (bg) */
+			UI_draw_roundbox_corner_set(UI_CNR_ALL);
+			UI_draw_roundbox_aa(
+			        true,
+			        posit[0] - bg_margin,                  posit[1] - bg_margin,
+			        posit[0] + bg_margin + numstr_size[0], posit[1] + bg_margin + numstr_size[1],
+			        bg_radius, color_back);
+			/* draw text */
+			BLF_color3ubv(blf_mono_font, color_text);
+			BLF_position(blf_mono_font, posit[0], posit[1], 0.0f);
+			BLF_rotation(blf_mono_font, 0.0f);
+			BLF_draw(blf_mono_font, numstr, sizeof(numstr));
+		}
+	}
+	else {
+		immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);
+
+		float viewport_size[4];
+		glGetFloatv(GL_VIEWPORT, viewport_size);
+		immUniform2f("viewport_size", viewport_size[2], viewport_size[3]);
+
+		immUniform1i("num_colors", 2);  /* "advanced" mode */
+		const float *col = is_act ? color_act : color_base;
+		immUniformArray4fv("colors", (float *)(float[][4]){{0.67f, 0.67f, 0.67f, 1.0f}, {col[0], col[1], col[2], col[3]}}, 2);
+		immUniform1f("dash_width", 6.0f);
+
+		immBegin(GWN_PRIM_LINES, 2);
+
+		immVertex2fv(shdr_pos, co_ss[0]);
+		immVertex2fv(shdr_pos, co_ss[2]);
+
+		immEnd();
+
+		immUnbindProgram();
+
+		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+
+		sub_v2_v2v2(dir_ruler, co_ss[0], co_ss[2]);
+
+		/* capping */
+		{
+			float rot_90_vec[2] = {-dir_ruler[1], dir_ruler[0]};
+			float cap[2];
+
+			normalize_v2(rot_90_vec);
+
+			glEnable(GL_BLEND);
+
+			immUniformColor3ubv(color_wire);
+
+			immBegin(GWN_PRIM_LINES, 4);
+
+			madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec, cap_size);
+			immVertex2fv(shdr_pos, cap);
+			madd_v2_v2v2fl(cap, co_ss[0], rot_90_vec, -cap_size);
+			immVertex2fv(shdr_pos, cap);
+
+			madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec, cap_size);
+			immVertex2fv(shdr_pos, cap);
+			madd_v2_v2v2fl(cap, co_ss[2], rot_90_vec, -cap_size);
+			immVertex2fv(shdr_pos, cap);
+
+			immEnd();
+
+			glDisable(GL_BLEND);
+		}
+
+		immUnbindProgram();
+
+		/* text */
+		{
+			char numstr[256];
+			float numstr_size[2];
+			const int prec = 6;  /* XXX, todo, make optional */
+			float posit[2];
+
+			ruler_item_as_string(ruler_item, unit, numstr, sizeof(numstr), prec);
+
+			BLF_width_and_height(blf_mono_font, numstr, sizeof(numstr), &numstr_size[0], &numstr_size[1]);
+
+			mid_v2_v2v2(posit, co_ss[0], co_ss[2]);
+
+			/* center text */
+			posit[0] -= numstr_size[0] / 2.0f;
+			posit[1] -= numstr_size[1] / 2.0f;
+
+			/* draw text (bg) */
+			UI_draw_roundbox_corner_set(UI_CNR_ALL);
+			UI_draw_roundbox_aa(
+			        true,
+			        posit[0] - bg_margin,                  posit[1] - bg_margin,
+			        posit[0] + bg_margin + numstr_size[0], posit[1] + bg_margin + numstr_size[1],
+			        bg_radius, color_back);
+			/* draw text */
+			BLF_color3ubv(blf_mono_font, color_text);
+			BLF_position(blf_mono_font, posit[0], posit[1], 0.0f);
+			BLF_draw(blf_mono_font, numstr, sizeof(numstr));
+		}
+	}
+
+	glDisable(GL_LINE_SMOOTH);
+
+	BLF_disable(blf_mono_font, BLF_ROTATION);
+
+#undef ARC_STEPS
+
+	/* draw snap */
+	if ((ruler_info->snap_flag & RULER_SNAP_OK) &&
+	    (ruler_info->state == RULER_STATE_DRAG) &&
+	    (ruler_item->mpr.interaction_data != NULL))
+	{
+		RulerInteraction *inter = ruler_item->mpr.interaction_data;
+		/* size from drawSnapping */
+		const float size = 2.5f * UI_GetThemeValuef(TH_VERTEX_SIZE);
+		float co_ss_snap[3];
+		ED_view3d_project_float_global(ar, ruler_item->co[inter->co_index], co_ss_snap, V3D_PROJ_TEST_NOP);
+
+		unsigned int pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+
+		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+		immUniformColor4fv(color_act);
+
+		imm_draw_circle_wire_2d(pos, co_ss_snap[0], co_ss_snap[1], size * U.pixelsize, 32);
+
+		immUnbindProgram();
+	}
+}
+
+static int manipulator_ruler_test_select(
+        bContext *UNUSED(C), wmManipulator *mpr, const wmEvent *event)
+{
+	RulerItem *ruler_item_pick = (RulerItem *)mpr;
+	float mval_fl[2] = {UNPACK2(event->mval)};
+	int co_index;
+
+	/* select and drag */
+	if (view3d_ruler_pick(mpr->parent_mgroup, ruler_item_pick, mval_fl, &co_index)) {
+		if (co_index == -1) {
+			if ((ruler_item_pick->flag & RULERITEM_USE_ANGLE) == 0) {
+				return PART_LINE;
+			}
+		}
+		else {
+			return co_index;
+		}
+	}
+	return -1;
+}
+
+static int manipulator_ruler_modal(
+        bContext *C, wmManipulator *mpr, const wmEvent *event,
+        eWM_ManipulatorTweak UNUSED(tweak_flag))
+{
+	bool do_draw = false;
+	int exit_code = OPERATOR_RUNNING_MODAL;
+	RulerInfo *ruler_info = mpr->parent_mgroup->customdata;
+	RulerItem *ruler_item = (RulerItem *)mpr;
+	RulerInteraction *inter = ruler_item->mpr.interaction_data;
+	ARegion *ar = CTX_wm_region(C);
+
+	ruler_info->ar = ar;
+
+	switch (event->type) {
+		case MOUSEMOVE:
+		{
+			if (ruler_info->state == RULER_STATE_DRAG) {
+				if (view3d_ruler_item_mousemove(
+				        ruler_info, ruler_item, event->mval,
+				        event->shift != 0, event->ctrl != 0))
+				{
+					do_draw = true;
+				}
+				inter->inside_region = BLI_rcti_isect_pt_v(&ar->winrct, &event->x);
+			}
+			break;
+		}
+	}
+	if (do_draw) {
+		ED_region_tag_redraw(ar);
+	}
+	return exit_code;
+}
+
+static int manipulator_ruler_invoke(
+        bContext *C, wmManipulator *mpr, const wmEvent *event)
+{
+	wmManipulatorGroup *mgroup = mpr->parent_mgroup;
+	RulerInfo *ruler_info = mgroup->customdata;
+	RulerItem *ruler_item_pick = (RulerItem *)mpr;
+	RulerInteraction *inter = MEM_callocN(sizeof(RulerInteraction), __func__);
+	mpr->interaction_data = inter;
+
+	ARegion *ar = ruler_info->ar;
+
+	const float mval_fl[2] = {UNPACK2(event->mval)};
+
+	/* select and drag */
+	if (mpr->highlight_part == PART_LINE) {
+		if ((ruler_item_pick->flag & RULERITEM_USE_ANGLE) == 0) {
+			/* Add Center Point */
+			ruler_item_pick->flag |= RULERITEM_USE_ANGLE;
+			inter->co_index = 1;
+			ruler_state_set(C, ruler_info, RULER_STATE_DRAG);
+
+			/* find the factor */
+			{
+				float co_ss[2][2];
+				float fac;
+
+				ED_view3d_project_float_global(ar, ruler_item_pick->co[0], co_ss[0], V3D_PROJ_TEST_NOP);
+				ED_view3d_project_float_global(ar, ruler_item_pick->co[2], co_ss[1], V3D_PROJ_TEST_NOP);
+
+				fac = line_point_factor_v2(mval_fl, co_ss[0], co_ss[1]);
+				CLAMP(fac, 0.0f, 1.0f);
+
+				interp_v3_v3v3(ruler_item_pick->co[1],
+				               ruler_item_pick->co[0],
+				               ruler_item_pick->co[2], fac);
+			}
+
+			/* update the new location */
+			view3d_ruler_item_mousemove(
+			        ruler_info, ruler_item_pick, event->mval,
+			        event->shift != 0, event->ctrl != 0);
+		}
+	}
+	else {
+		inter->co_index = mpr->highlight_part;
+		ruler_state_set(C, ruler_info, RULER_STATE_DRAG);
+
+		/* store the initial depth */
+		copy_v3_v3(inter->drag_start_co, ruler_item_pick->co[inter->co_index]);
+	}
+
+	return OPERATOR_RUNNING_MODAL;
+}
+
+static void manipulator_ruler_exit(bContext *C, wmManipulator *mpr, const bool cancel)
+{
+	wmManipulatorGroup *mgroup = mpr->parent_mgroup;
+	RulerInfo *ruler_info = mgroup->customdata;
+	RulerItem *ruler_item = (RulerItem *)mpr;
+	RulerInteraction *inter = mpr->interaction_data;
+
+	if (!cancel) {
+		if (ruler_info->state == RULER_STATE_DRAG) {
+			/* rubber-band angle removal */
+			if (ruler_item && (inter->co_index == 1) && (ruler_item->flag & RULERITEM_USE_ANGLE)) {
+				if (!inter->inside_region) {
+					ruler_item->flag &= ~RULERITEM_USE_ANGLE;
+				}
+			}
+			if (ruler_info->snap_flag & RULER_SNAP_OK) {
+				ruler_info->snap_flag &= ~RULER_SNAP_OK;
+			}
+			ruler_state_set(C, ruler_info, RULER_STATE_NORMAL);
+		}
+		/* We could convert only the current manipulator, for now just re-generate. */
+		view3d_ruler_to_gpencil(C, mgroup);
+	}
+
+	MEM_SAFE_FREE(mpr->interaction_data);
+
+	ruler_state_set(C, ruler_info, RULER_STATE_NORMAL);
+}
+
+static int manipulator_ruler_cursor_get(wmManipulator *mpr)
+{
+	if (mpr->highlight_part == PART_LINE) {
+		return BC_CROSSCURSOR;
+	}
+	return BC_NSEW_SCROLLCURSOR;
+}
+
+void VIEW3D_WT_ruler_item(wmManipulatorType *wt)
+{
+	/* identifiers */
+	wt->idname = "VIEW3D_WT_ruler_item";
+
+	/* api callbacks */
+	wt->draw = manipulator_ruler_draw;
+	wt->test_select = manipulator_ruler_test_select;
+	wt->modal = manipulator_ruler_modal;
+	wt->invoke = manipulator_ruler_invoke;
+	wt->exit = manipulator_ruler_exit;
+	wt->cursor_get = manipulator_ruler_cursor_get;
+
+	wt->struct_size = sizeof(RulerItem);
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Ruler Manipulator Group
+ * \{ */
+
+static bool WIDGETGROUP_ruler_poll(const bContext *C, wmManipulatorGroupType *wgt)
+{
+	WorkSpace *workspace = CTX_wm_workspace(C);
+	if (!STREQ(wgt->idname, workspace->tool.manipulator_group)) {
+		WM_manipulator_group_type_unlink_delayed_ptr(wgt);
+		return false;
+	}
+	return true;
+}
+
+static void WIDGETGROUP_ruler_setup(const bContext *C, wmManipulatorGroup *mgroup)
+{
+	RulerInfo *ruler_info = MEM_callocN(sizeof(RulerInfo), __func__);
+
+	if (view3d_ruler_from_gpencil(C, mgroup)) {
+		/* nop */
+	}
+
+	wmWindow *win = CTX_wm_window(C);
+	ScrArea *sa = CTX_wm_area(C);
+	ARegion *ar = CTX_wm_region(C);
+	ruler_info->win = win;
+	ruler_info->sa = sa;
+	ruler_info->ar = ar;
+
+	mgroup->customdata = ruler_info;
+}
+
+void VIEW3D_WGT_ruler(wmManipulatorGroupType *wgt)
+{
+	wgt->name = "Ruler Widgets";
+	wgt->idname = view3d_wgt_ruler_id;
+
+	wgt->flag |= WM_MANIPULATORGROUPTYPE_SCALE;
+
+	wgt->mmap_params.spaceid = SPACE_VIEW3D;
+	wgt->mmap_params.regionid = RGN_TYPE_WINDOW;
+
+	wgt->poll = WIDGETGROUP_ruler_poll;
+	wgt->setup = WIDGETGROUP_ruler_setup;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Add Ruler Operator
+ * \{ */
+
+static int view3d_ruler_poll(bContext *C)
+{
+	WorkSpace *workspace = CTX_wm_workspace(C);
+	if (!STREQ(view3d_wgt_ruler_id, workspace->tool.manipulator_group) ||
+	    CTX_wm_region_view3d(C) == NULL)
+	{
+		return false;
+	}
+	return true;
+}
+
+static int view3d_ruler_add_invoke(bContext *C, wmOperator *UNUSED(op), const wmEvent *event)
+{
+	ARegion *ar = CTX_wm_region(C);
+	View3D *v3d = CTX_wm_view3d(C);
+	RegionView3D *rv3d = ar->regiondata;
+
+	wmManipulatorMap *mmap = ar->manipulator_map;
+	wmManipulatorGroup *mgroup = WM_manipulatormap_group_find(mmap, view3d_wgt_ruler_id);
+	const bool use_depth = (v3d->drawtype >= OB_SOLID);
+
+	/* Create new line */
+	RulerItem *ruler_item;
+	ruler_item = ruler_item_add(mgroup);
+
+	/* This is a little weak, but there is no real good way to tweak directly. */
+	WM_manipulator_highlight_set(mmap, &ruler_item->mpr);
+	if (WM_operator_name_call(
+	        C, "MANIPULATORGROUP_OT_manipulator_tweak",
+	        WM_OP_INVOKE_REGION_WIN, NULL) == OPERATOR_RUNNING_MODAL)
+	{
+		RulerInfo *ruler_info = mgroup->customdata;
+		RulerInteraction *inter = ruler_item->mpr.interaction_data;
+		if (use_depth) {
+			/* snap the first point added, not essential but handy */
+			inter->co_index = 0;
+			view3d_ruler_item_mousemove(ruler_info, ruler_item, event->mval, false, true);
+			copy_v3_v3(inter->drag_start_co, ruler_item->co[inter->co_index]);
+		}
+		else {
+			negate_v3_v3(inter->drag_start_co, rv3d->ofs);
+			copy_v3_v3(ruler_item->co[0], inter->drag_start_co);
+			view3d_ruler_item_project(ruler_info, ruler_item->co[0], event->mval);
+		}
+
+		copy_v3_v3(ruler_item->co[2], ruler_item->co[0]);
+		ruler_item->mpr.highlight_part = inter->co_index = 2;
+	}
+	return OPERATOR_FINISHED;
+}
+
+void VIEW3D_OT_ruler_add(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Ruler Add";
+	ot->idname = "VIEW3D_OT_ruler_add";
+	ot->description = "";
+
+	ot->invoke = view3d_ruler_add_invoke;
+	ot->poll = view3d_ruler_poll;
+
+	/* flags */
+	ot->flag = OPTYPE_UNDO | OPTYPE_INTERNAL;
+}
+
+/** \} */
diff --git a/source/blender/editors/space_view3d/view3d_ops.c b/source/blender/editors/space_view3d/view3d_ops.c
index ddba3c69320..568343f8ec8 100644
--- a/source/blender/editors/space_view3d/view3d_ops.c
+++ b/source/blender/editors/space_view3d/view3d_ops.c
@@ -222,6 +222,8 @@ void view3d_operatortypes(void)
 
 	WM_operatortype_append(VIEW3D_OT_toggle_render);
 
+	WM_operatortype_append(VIEW3D_OT_ruler_add);
+
 	transform_operatortypes();
 }