WIP: VFONT: Text Selection Operator

An operator to allow interactive text selection for 3D Text Objects.
This is largely the code of Yash Dabhade (yashdabhade) for GSoC 2022
with corrections and simplifications.

@@ -780,2 +780,3 @@
                            bool *r_text_free,
-                           struct CharTrans **r_chartransdata)
+                           struct CharTrans **r_chartransdata,
+                           float cursor_location[2],

@@ -781,1 +781,3 @@
-                           struct CharTrans **r_chartransdata)
+                           struct CharTrans **r_chartransdata,
+                           float cursor_location[2],
+                           int *r_caret_pos)

@@ -914,0 +916,4 @@
+
+  int caret_pos = -1;
+  float caret_pos_min_dist = 0;
+  if (cursor_location && ef != NULL && ob != NULL) {

@@ -1128,0 +1139,4 @@
+
+    if (cursor_location) {
+      float offset_loc[2] = {cursor_location[0] - xof, cursor_location[1] - yof};
+      float di = len_squared_v2(offset_loc);

@@ -1128,0 +1140,4 @@
+    if (cursor_location) {
+      float offset_loc[2] = {cursor_location[0] - xof, cursor_location[1] - yof};
+      float di = len_squared_v2(offset_loc);
+      float di2 = len_squared_v2(cursor_location);

@@ -1799,0 +1824,4 @@
+  ef = cu->editfont;
+  BLI_assert(ef->len >= 0);
+
+  cur_loc_pos = BKE_vfont_cursor_to_caret_pos(ob, curs_loc);

@@ -734,6 +734,14 @@ typedef struct VFontToCurveIter {
   int status;
 } VFontToCurveIter;
 
+/* Used when translating a mouse cursor location to a position within the string. */

@@ -736,1 +736,4 @@
 
+/* Used when translating a mouse cursor location to a position within the string. */
+typedef struct VFontCursor_Params {
+  /* Mouse cursor location as input. */

@@ -737,0 +738,4 @@
+typedef struct VFontCursor_Params {
+  /* Mouse cursor location as input. */
+  float cursor_location[2];
+  /* string character position as output. */

@@ -780,2 +788,3 @@
                            bool *r_text_free,
-                           struct CharTrans **r_chartransdata)
+                           struct CharTrans **r_chartransdata,
+                           struct VFontCursor_Params *cursor_params)

@@ -912,2 +921,4 @@
 
   i = 0;
+
+  float cursor_min_dist = 0;

@@ -914,0 +925,4 @@
+  float cursor_sq_dist = 0;
+  if (cursor_params) {
+    cursor_params->r_string_offset = -1;
+    cursor_sq_dist = len_squared_v2(cursor_params->cursor_location);

@@ -1128,0 +1148,4 @@
+      float offset_loc[2] = {cursor_params->cursor_location[0] - xof,
+                             cursor_params->cursor_location[1] - yof};
+      float cursor_sq_offset = len_squared_v2(offset_loc);
+      if (cursor_sq_dist <= cursor_min_dist && cursor_sq_dist < cursor_sq_offset) {

@@ -1799,0 +1824,4 @@
+  ef = cu->editfont;
+  BLI_assert(ef->len >= 0);
+
+  cur_loc_pos = BKE_vfont_cursor_to_string_offset(ob, curs_loc);

@@ -1799,0 +1871,4 @@
+static int font_selection_set_modal(bContext *C, wmOperator *UNUSED(op), const wmEvent *event)
+{
+  switch (event->type) {
+    case LEFTMOUSE: // release

@@ -73,2 +73,4 @@
                            struct CharTrans **r_chartransdata);
 bool BKE_vfont_to_curve_nubase(struct Object *ob, int mode, struct ListBase *r_nubase);
+
+int BKE_vfont_cursor_to_string_offset(struct Object *ob, float cursor_location[2]);

@@ -914,0 +933,4 @@
+  float cursor_sq_dist_test = 0;
+  if (cursor_params) {
+    cursor_params->r_string_offset = -1;
+    cursor_sq_dist_test = len_squared_v2(cursor_params->cursor_location);

@@ -1128,0 +1162,4 @@
+      }
+      else if (cursor_sq_dist_test < cursor_sq_dist_best) {
+        /* Left of text, including left-side of first character. */
+        cursor_params->r_string_offset = -1;

@@ -1799,0 +1806,4 @@
+  Curve *cu = obedit->data;
+  EditFont *ef = cu->editfont;
+
+  /* Calculate a plane from the text object's orientation. */

@@ -737,0 +741,4 @@
+ * This is an optional argument to `vfont_to_curve` for getting the text
+ * offset into the string at a mouse cursor location. Used for getting
+ * text cursor (caret) position or selection range.
+ * \{ */

@@ -911,6 +928,7 @@ static bool vfont_to_curve(Object *ob,
   }
 
   i = 0;
+

@@ -1796,6 +1796,148 @@ void FONT_OT_text_insert(wmOperatorType *ot)
 
 /** \} */
 
+static void font_cursor_text_index_from_event(bContext *C,

@@ -1799,0 +1820,4 @@
+  r_curs_loc[1] = mouse_loc[1] / cu->fsize;
+}
+
+/* -------------------------------------------------------------------- */

@@ -1128,0 +1146,4 @@
+
+    if (cursor_params) {
+      float midw = (twidth / 2.0f);
+      if (cursor_params->cursor_location[1] >= yof - (0.25f * linedist) &&

@@ -5611,6 +5611,7 @@ def km_font(params):
          {"properties": [("delta", 1)]}),
         ("font.change_character", {"type": 'DOWN_ARROW', "value": 'PRESS', "alt": True, "repeat": True},
          {"properties": [("delta", -1)]}),
+        ("font.select_word", {"type": 'LEFTMOUSE', "value": 'DOUBLE_CLICK'}, None),

@@ -1262,0 +1269,4 @@
+            cursor='CROSSHAIR',
+            icon="ops.generic.select_box",
+            widget=None,
+            keymap=("3D View Tool: Text Select"),