UI: improve percentage display for wm.progress API

wm.progress displayed a percentage in a cryptic
2x2 grid of numbers, so:

```
75
23
```

Represents `75.23%`. This is now shown as `75.23%`
on systems that support RGBA cursors.

source/blender/makesrna/intern/rna_wm_api.cc

@@ -201,12 +201,12 @@ static void rna_progress_begin(wmWindowManager * /*wm*/, float min, float max)
 static void rna_progress_update(wmWindowManager *wm, float value)
 {
   if (wm_progress_state.is_valid) {
-    /* Map to cursor_time range [0,9999] */
+    /* Map to factor 0..1. */
     wmWindow *win = wm->winactive;
     if (win) {
-      int val = int(10000 * (value - wm_progress_state.min) /
-                    (wm_progress_state.max - wm_progress_state.min));
-      WM_cursor_time(win, val);
+      const float progress_factor = (value - wm_progress_state.min) /
+                                    (wm_progress_state.max - wm_progress_state.min);
+      WM_cursor_progress(win, progress_factor);
     }
   }
 }

source/blender/windowmanager/WM_api.hh

@@ -527,6 +527,11 @@ void WM_cursor_grab_disable(wmWindow *win, const int mouse_ungrab_xy[2]);
  */
 void WM_cursor_time(wmWindow *win, int nr);
 
+/**
+ * Show progress in the cursor (0.0..1.0 when complete).
+ */
+void WM_cursor_progress(wmWindow *win, float progress_factor);
+
 wmPaintCursor *WM_paint_cursor_activate(short space_type,
                                         short region_type,
                                         bool (*poll)(bContext *C),

source/blender/windowmanager/intern/wm_cursors.cc

@@ -52,6 +52,12 @@
  */
 constexpr int CURSOR_HARDWARE_SIZE_MAX = 255;
 
+/**
+ * The maximum size of cursor text (in bytes).
+ * Can remain small as it's unlikely we can ever show much text in a cursor.
+ */
+#define CURSOR_TEXT_BUFFER_SIZE 24
+
 /** Blender custom cursor. */
 struct BCursor {
   /**
@@ -729,7 +735,7 @@ static void wm_cursor_time_small(wmWindow *win, uint32_t nr)
  * \return the pixel data as a `sizeof(uint8_t[4]) * r_bitmap_size[0] * r_bitmap_size[1]` array
  * or null on failure.
  */
-static uint8_t *cursor_bitmap_from_text(const std::string &text,
+static uint8_t *cursor_bitmap_from_text(const char *text,
                                         const int cursor_size,
                                         const int cursor_size_max,
                                         int font_id,
@@ -746,8 +752,9 @@ static uint8_t *cursor_bitmap_from_text(const std::string &text,
   int font_descender;
 
   /* At least 1 even on an empty string else the cursor is blank. */
-  const int text_units = std::max(1, BLI_str_utf8_column_count(text.c_str(), text.size()));
-  const bool text_to_draw = text.size() > 0;
+  const size_t text_len = strlen(text);
+  const int text_units = std::max(1, BLI_str_utf8_column_count(text, text_len));
+  const bool text_to_draw = text_len != 0;
 
   for (int pass = 0; pass < 2; pass++) {
     BLF_size(font_id, font_size);
@@ -791,7 +798,7 @@ static uint8_t *cursor_bitmap_from_text(const std::string &text,
     BLF_buffer_col(font_id, color);
     BLF_buffer(font_id, nullptr, bitmap_rgba, dest_size[0], dest_size[1], nullptr);
     BLF_position(font_id, font_padding, font_padding + font_descender, 0.0f);
-    BLF_draw_buffer(font_id, text.c_str(), text.size());
+    BLF_draw_buffer(font_id, text, text_len);
     BLF_buffer(font_id, nullptr, nullptr, 0, 0, nullptr);
 
     cursor_bitmap_rgba_flip_y(bitmap_rgba, dest_size);
@@ -803,10 +810,10 @@ static uint8_t *cursor_bitmap_from_text(const std::string &text,
   return bitmap_rgba;
 }
 
-static bool wm_cursor_text_generator(wmWindow *win, const std::string &text, int font_id)
+static bool wm_cursor_text_generator(wmWindow *win, const char *text, int font_id)
 {
   struct WMCursorText {
-    std::string text;
+    char text[CURSOR_TEXT_BUFFER_SIZE];
     int font_id;
   };
 
@@ -845,7 +852,7 @@ static bool wm_cursor_text_generator(wmWindow *win, const std::string &text, int
   };
 
   WMCursorText *cursor_text = MEM_new<WMCursorText>(__func__);
-  cursor_text->text = text;
+  STRNCPY_UTF8(cursor_text->text, text);
   cursor_text->font_id = font_id;
 
   cursor_generator->user_data = (void *)cursor_text;
@@ -861,7 +868,7 @@ static bool wm_cursor_text_generator(wmWindow *win, const std::string &text, int
   return (success == GHOST_kSuccess) ? true : false;
 }
 
-static bool wm_cursor_text_pixmap(wmWindow *win, const std::string &text, int font_id)
+static bool wm_cursor_text_pixmap(wmWindow *win, const char *text, int font_id)
 {
   const int cursor_size = wm_cursor_size(win);
   /* This is arbitrary. Use a larger value than the cursor size since the text is often wider than
@@ -899,7 +906,7 @@ static bool wm_cursor_text_pixmap(wmWindow *win, const std::string &text, int fo
   return (success == GHOST_kSuccess) ? true : false;
 }
 
-static bool wm_cursor_text(wmWindow *win, const std::string &text, int font_id)
+static bool wm_cursor_text(wmWindow *win, const char *text, int font_id)
 {
   if (WM_capabilities_flag() & WM_CAPABILITY_CURSOR_GENERATOR) {
     return wm_cursor_text_generator(win, text, font_id);
@@ -907,7 +914,11 @@ static bool wm_cursor_text(wmWindow *win, const std::string &text, int font_id)
   return wm_cursor_text_pixmap(win, text, font_id);
 }
 
-void WM_cursor_time(wmWindow *win, int nr)
+/**
+ * \param is_percentage: When true, nr represents a percentage multiplied by 100
+ * so the percentage with two decimal places can be shown.
+ */
+static void wm_cursor_number_impl(wmWindow *win, int nr, bool is_percentage)
 {
   if (win->lastcursor == 0) {
     win->lastcursor = win->cursor;
@@ -919,7 +930,15 @@ void WM_cursor_time(wmWindow *win, int nr)
   const uint32_t nr_abs = nr >= 0 ? uint32_t(nr) : -uint32_t(nr);
 
   if (WM_capabilities_flag() & WM_CAPABILITY_CURSOR_RGBA) {
-    wm_cursor_text(win, std::to_string(nr_abs), blf_mono_font);
+    char text[CURSOR_TEXT_BUFFER_SIZE];
+    if (is_percentage) {
+      /* Left pad to avoid resizing text between 9% & 10%. */
+      SNPRINTF_UTF8(text, "%2u.%02u", nr_abs / 100, nr_abs % 100);
+    }
+    else {
+      SNPRINTF_UTF8(text, "%u", nr_abs);
+    }
+    wm_cursor_text(win, text, blf_mono_font);
   }
   else if (wm_cursor_size(win) < 24 || !wm_cursor_time_large(win, nr_abs)) {
     wm_cursor_time_small(win, nr_abs);
@@ -929,6 +948,18 @@ void WM_cursor_time(wmWindow *win, int nr)
   win->cursor = 0;
 }
 
+void WM_cursor_time(wmWindow *win, int nr)
+{
+  wm_cursor_number_impl(win, nr, false);
+}
+
+void WM_cursor_progress(wmWindow *win, float progress_factor)
+{
+  constexpr int nr_max = 10000;
+  const int nr = std::clamp(int(std::round(double(progress_factor) * nr_max)), 0, nr_max);
+  wm_cursor_number_impl(win, nr, true);
+}
+
 #ifndef WITH_HEADLESS
 static void wm_add_cursor(WMCursorType cursor,
                           const char *svg_source,