UI: Fix time labels drawing

Calculate frequency of time/frame label drawing, such that labels have
at least 10px margin and don't overlap.

Change timecode format:
- Use at least `mm:ss` format
- Don't display frames if all labels would end with +00

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D11792

source/blender/blenlib/intern/timecode.c

@@ -115,7 +115,7 @@ size_t BLI_timecode_string_from_time(char *str,
               str, maxncpy, "%s%02d:%02d+%02d", neg, minutes, seconds, frames);
         }
         else {
-          rlen = BLI_snprintf_rlen(str, maxncpy, "%s%d+%02d", neg, seconds, frames);
+          rlen = BLI_snprintf_rlen(str, maxncpy, "%s00:%02d+%02d", neg, seconds, frames);
         }
       }
       else {

source/blender/editors/interface/view2d_draw.c

@@ -326,10 +326,27 @@ static void draw_horizontal_scale_indicators(const ARegion *region,
   const float xmin = rect->xmin;
   const float xmax = rect->xmax;
 
-  for (uint i = 0; i < steps; i++) {
+  char text[32];
+
+  /* Calculate max_label_count and draw_frequency based on largest visible label. */
+  to_string(to_string_data, start, 0, sizeof(text), text);
+  const float left_text_width = BLF_width(font_id, text, strlen(text));
+  to_string(to_string_data, start + steps * distance, 0, sizeof(text), text);
+  const float right_text_width = BLF_width(font_id, text, strlen(text));
+  const float max_text_width = max_ff(left_text_width, right_text_width);
+  const float max_label_count = BLI_rcti_size_x(&v2d->mask) / (max_text_width + 10.0f);
+  const int draw_frequency = ceil((float)steps / max_label_count);
+
+  if (draw_frequency == 0) {
+    BLF_batch_draw_end();
+    GPU_matrix_pop_projection();
+    return;
+  }
+
+  const int start_index = abs(start / distance) % draw_frequency;
+  for (uint i = start_index; i < steps; i += draw_frequency) {
     const float xpos_view = start + i * distance;
     const float xpos_region = UI_view2d_view_to_region_x(v2d, xpos_view);
-    char text[32];
     to_string(to_string_data, xpos_view, distance, sizeof(text), text);
     const float text_width = BLF_width(font_id, text, strlen(text));
 
@@ -339,7 +356,6 @@ static void draw_horizontal_scale_indicators(const ARegion *region,
   }
 
   BLF_batch_draw_end();
-
   GPU_matrix_pop_projection();
 }
 
@@ -413,11 +429,15 @@ static void view_to_string__frame_number(
 }
 
 static void view_to_string__time(
-    void *user_data, float v2d_pos, float UNUSED(v2d_step), uint max_len, char *r_str)
+    void *user_data, float v2d_pos, float v2d_step, uint max_len, char *r_str)
 {
   const Scene *scene = (const Scene *)user_data;
 
-  const int brevity_level = 0;
+  int brevity_level = 0;
+  if (U.timecode_style == USER_TIMECODE_MINIMAL && v2d_step >= FPS) {
+    brevity_level = 1;
+  }
+
   BLI_timecode_string_from_time(
       r_str, max_len, brevity_level, v2d_pos / (float)FPS, FPS, U.timecode_style);
 }