VSE: Strip drawing improvements

This patch include changes:
- Thicker and clearer selection indication
- Slimmer handles
- More transparent muted strips
- Trim frame number is drawn inside the strip
- Strip text is drawn in upper part of strip
- Color strips now have specific color, with chosen color drawn under strip text
- Transition strip will use color of input strips showing direction of transition
- Selecting effect strip will highlight input strips
- Selecting multicam strips will highlight target channel
- Missing media state is now indicated by a red line drawn on the top part of the strip
- A checkerboard pattern is now drawn on the outsides of the meta range
- Hold still regions are now always drawn if existent, with a darker shade of the strip’s background color

Author: Alessio Monti di Sopra <a.monti>

Reviewed By: ISS

Differential Revision: https://developer.blender.org/D6883

source/blender/editors/space_sequencer/CMakeLists.txt

@@ -17,6 +17,7 @@
 
 set(INC
   ../include
+  ../../blenfont
   ../../blenkernel
   ../../blenlib
   ../../blentranslation

source/blender/editors/space_sequencer/sequencer_edit.c

@@ -407,7 +407,7 @@ Sequence *find_nearest_seq(Scene *scene, View2D *v2d, int *hand, const int mval[
 
           /* clamp handles to defined size in pixel space */
 
-          handsize = seq->handsize;
+          handsize = 2.0f * sequence_handle_size_get_clamped(seq, pixelx);
           displen = (float)abs(seq->startdisp - seq->enddisp);
 
           /* don't even try to grab the handles of small strips */

source/blender/editors/space_sequencer/sequencer_select.c

@@ -1044,7 +1044,7 @@ static int sequencer_box_select_exec(bContext *C, wmOperator *op)
       if (handles) {
         /* Get the handles draw size. */
         float pixelx = BLI_rctf_size_x(&v2d->cur) / BLI_rcti_size_x(&v2d->mask);
-        float handsize = sequence_handle_size_get_clamped(seq, pixelx) * 0.75f;
+        float handsize = sequence_handle_size_get_clamped(seq, pixelx);
 
         /* Right handle. */
         if (rectf.xmax > (seq->enddisp - handsize)) {