Sequencer: Implement zoom-to-fit view mode

In this mode the preview image is always using the most of the preview
area space: it is scaled to fit, preserving aspect ratio. This makes it
possible to always have maximum of the preview region even after resize
of other areas.

This mode is enabled by default, is available in the View -> Zoom to Fit
menu. It is enabled when View All (Home key) is used, and is disabled
when manual navigation ([panning, zooming) is performed.

There is no versioning code, which means existing files will open as-is,
but new projects will have this option enabled.

Ref T78987

Maniphest Tasks: T78987

Differential Revision: https://developer.blender.org/D8549

2 files changed, 25 insertions, 2 deletions

diff --git a/source/blender/editors/space_sequencer/sequencer_view.c b/source/blender/editors/space_sequencer/sequencer_view.c
index 2b9370970de..491c475b596 100644
--- a/source/blender/editors/space_sequencer/sequencer_view.c
+++ b/source/blender/editors/space_sequencer/sequencer_view.c
@@ -144,11 +144,11 @@ void SEQUENCER_OT_view_frame(wmOperatorType *ot)
 
 static int sequencer_view_all_preview_exec(bContext *C, wmOperator *UNUSED(op))
 {
+  SpaceSeq *sseq = CTX_wm_space_seq(C);
   bScreen *screen = CTX_wm_screen(C);
   ScrArea *area = CTX_wm_area(C);
 #if 0
   ARegion *region = CTX_wm_region(C);
-  SpaceSeq *sseq = area->spacedata.first;
   Scene *scene = CTX_data_scene(C);
 #endif
   View2D *v2d = UI_view2d_fromcontext(C);
@@ -186,6 +186,8 @@ static int sequencer_view_all_preview_exec(bContext *C, wmOperator *UNUSED(op))
   }
 #endif
 
+  sseq->flag |= SEQ_ZOOM_TO_FIT;
+
   ED_area_tag_redraw(CTX_wm_area(C));
   return OPERATOR_FINISHED;
 }
@@ -228,6 +230,8 @@ static int sequencer_view_zoom_ratio_exec(bContext *C, wmOperator *op)
 
   ED_region_tag_redraw(CTX_wm_region(C));
 
+  UI_view2d_curRect_changed(C, v2d);
+
   return OPERATOR_FINISHED;
 }
 
diff --git a/source/blender/editors/space_sequencer/space_sequencer.c b/source/blender/editors/space_sequencer/space_sequencer.c
index b8bb3e4d43b..4a6bd0de60c 100644
--- a/source/blender/editors/space_sequencer/space_sequencer.c
+++ b/source/blender/editors/space_sequencer/space_sequencer.c
@@ -96,7 +96,8 @@ static SpaceLink *sequencer_create(const ScrArea *UNUSED(area), const Scene *sce
   sseq->chanshown = 0;
   sseq->view = SEQ_VIEW_SEQUENCE;
   sseq->mainb = SEQ_DRAW_IMG_IMBUF;
-  sseq->flag = SEQ_SHOW_GPENCIL | SEQ_USE_ALPHA | SEQ_SHOW_MARKERS | SEQ_SHOW_FCURVES;
+  sseq->flag = SEQ_SHOW_GPENCIL | SEQ_USE_ALPHA | SEQ_SHOW_MARKERS | SEQ_SHOW_FCURVES |
+               SEQ_ZOOM_TO_FIT;
 
   /* Tool header. */
   region = MEM_callocN(sizeof(ARegion), "tool header for sequencer");
@@ -679,6 +680,22 @@ static void sequencer_preview_region_init(wmWindowManager *wm, ARegion *region)
   WM_event_add_keymap_handler_v2d_mask(&region->handlers, keymap);
 }
 
+static void sequencer_preview_region_layout(const bContext *C, ARegion *region)
+{
+  SpaceSeq *sseq = CTX_wm_space_seq(C);
+
+  if (sseq->flag & SEQ_ZOOM_TO_FIT) {
+    View2D *v2d = &region->v2d;
+    v2d->cur = v2d->tot;
+  }
+}
+
+static void sequencer_preview_region_view2d_changed(const bContext *C, ARegion *UNUSED(region))
+{
+  SpaceSeq *sseq = CTX_wm_space_seq(C);
+  sseq->flag &= ~SEQ_ZOOM_TO_FIT;
+}
+
 static void sequencer_preview_region_draw(const bContext *C, ARegion *region)
 {
   ScrArea *area = CTX_wm_area(C);
@@ -881,6 +898,8 @@ void ED_spacetype_sequencer(void)
   art = MEM_callocN(sizeof(ARegionType), "spacetype sequencer region");
   art->regionid = RGN_TYPE_PREVIEW;
   art->init = sequencer_preview_region_init;
+  art->layout = sequencer_preview_region_layout;
+  art->on_view2d_changed = sequencer_preview_region_view2d_changed;
   art->draw = sequencer_preview_region_draw;
   art->listener = sequencer_preview_region_listener;
   art->keymapflag = ED_KEYMAP_TOOL | ED_KEYMAP_GIZMO | ED_KEYMAP_VIEW2D | ED_KEYMAP_FRAMES |