Zoom to frame options, requested by the Hwoozeberry (dutch translation)

team.

There are 3 options here:

1) Keep range (previous behaviour)
2) Seconds - allows a specified offset in seconds around current frame
3) keyframes - zoom to include a number of keyframes around the cursor

Options 2 and 3 have their own properties to tweak the behaviour and all
options can be found in User Preferences->Interface under the 2D
viewports section.

Number 3 will probably need some refinement so commiting here for the
hwoozeberry team to test first.

6 files changed, 143 insertions, 18 deletions

diff --git a/source/blender/editors/animation/anim_draw.c b/source/blender/editors/animation/anim_draw.c
index 54d371d8f50..7d669e8c93e 100644
--- a/source/blender/editors/animation/anim_draw.c
+++ b/source/blender/editors/animation/anim_draw.c
@@ -34,17 +34,25 @@
 #include "DNA_scene_types.h"
 #include "DNA_space_types.h"
 #include "DNA_userdef_types.h"
+#include "DNA_screen_types.h"
+#include "DNA_object_types.h"
+#include "DNA_gpencil_types.h"
+#include "DNA_mask_types.h"
 
 #include "BLI_math.h"
 #include "BLI_timecode.h"
 #include "BLI_utildefines.h"
+#include "BLI_rect.h"
+#include "BLI_dlrbTree.h"
 
 #include "BKE_context.h"
 #include "BKE_global.h"
 #include "BKE_nla.h"
+#include "BKE_mask.h"
 
 #include "ED_anim_api.h"
 #include "ED_keyframes_edit.h"
+#include "ED_keyframes_draw.h"
 
 #include "RNA_access.h"
 
@@ -381,4 +389,136 @@ float ANIM_unit_mapping_get_factor(Scene *scene, ID *id, FCurve *fcu, short flag
 	return 1.0f;
 }
 
+static bool find_prev_next_keyframes(struct bContext *C, int *nextfra, int *prevfra) {
+	Scene *scene = CTX_data_scene(C);
+	Object *ob = CTX_data_active_object(C);
+	bGPdata *gpd = CTX_data_gpencil_data(C);
+	Mask *mask = CTX_data_edit_mask(C);
+	bDopeSheet ads = {NULL};
+	DLRBT_Tree keys;
+	ActKeyColumn *aknext, *akprev;
+	float cfranext, cfraprev;
+	bool donenext = false, doneprev = false;
+	int nextcount = 0, prevcount = 0;
+
+	cfranext = cfraprev = (float)(CFRA);
+
+	/* init binarytree-list for getting keyframes */
+	BLI_dlrbTree_init(&keys);
+
+	/* seed up dummy dopesheet context with flags to perform necessary filtering */
+	if ((scene->flag & SCE_KEYS_NO_SELONLY) == 0) {
+		/* only selected channels are included */
+		ads.filterflag |= ADS_FILTER_ONLYSEL;
+	}
+
+	/* populate tree with keyframe nodes */
+	scene_to_keylist(&ads, scene, &keys, NULL);
+
+	if (ob)
+		ob_to_keylist(&ads, ob, &keys, NULL);
+
+	gpencil_to_keylist(&ads, gpd, &keys);
+
+	if (mask) {
+		MaskLayer *masklay = BKE_mask_layer_active(mask);
+		mask_to_keylist(&ads, masklay, &keys);
+	}
+
+	/* build linked-list for searching */
+	BLI_dlrbTree_linkedlist_sync(&keys);
+
+	/* find matching keyframe in the right direction */
+	do {
+		aknext = (ActKeyColumn *)BLI_dlrbTree_search_next(&keys, compare_ak_cfraPtr, &cfranext);
+
+		if (aknext) {
+			if (CFRA == (int)aknext->cfra) {
+				/* make this the new starting point for the search and ignore */
+				cfranext = aknext->cfra;
+			}
+			else {
+				/* this changes the frame, so set the frame and we're done */
+				if (++nextcount == U.view_frame_keyframes)
+					donenext = true;
+			}
+			cfranext = aknext->cfra;
+		}
+	} while ((aknext != NULL) && (donenext == false));
+
+	do {
+		akprev = (ActKeyColumn *)BLI_dlrbTree_search_prev(&keys, compare_ak_cfraPtr, &cfraprev);
+
+		if (akprev) {
+			if (CFRA == (int)akprev->cfra) {
+				/* make this the new starting point for the search */
+			}
+			else {
+				/* this changes the frame, so set the frame and we're done */
+				if (++prevcount == U.view_frame_keyframes)
+					doneprev = true;
+			}
+			cfraprev = akprev->cfra;
+		}
+	} while ((akprev != NULL) && (doneprev == false));
+
+	/* free temp stuff */
+	BLI_dlrbTree_free(&keys);
+
+	/* any success? */
+	if (doneprev || donenext) {
+		if (doneprev)
+			*prevfra = cfraprev;
+		else
+			*prevfra = CFRA - (cfranext - CFRA);
+
+		if (donenext)
+			*nextfra = cfranext;
+		else
+			*nextfra = CFRA + (CFRA - cfraprev);
+
+		return true;
+	}
+
+	return false;
+}
+
+void ANIM_center_frame(struct bContext *C, int smooth_viewtx)
+{
+	ARegion *ar = CTX_wm_region(C);
+	Scene *scene = CTX_data_scene(C);
+	float w = BLI_rctf_size_x(&ar->v2d.cur);
+	rctf newrct;
+	int nextfra, prevfra;
+
+	switch (U.view_frame_type) {
+		case ZOOM_FRAME_MODE_SECONDS:
+			newrct.xmax = scene->r.cfra + U.view_frame_seconds * FPS + 1;
+			newrct.xmin = scene->r.cfra - U.view_frame_seconds * FPS - 1;
+			newrct.ymax = ar->v2d.cur.ymax;
+			newrct.ymin = ar->v2d.cur.ymin;
+			break;
+
+		/* hardest case of all, look for all keyframes around frame and display those */
+		case ZOOM_FRAME_MODE_KEYFRAMES:
+			if (find_prev_next_keyframes(C, &nextfra, &prevfra)) {
+				newrct.xmax = nextfra;
+				newrct.xmin = prevfra;
+				newrct.ymax = ar->v2d.cur.ymax;
+				newrct.ymin = ar->v2d.cur.ymin;
+				break;
+			}
+			/* else drop through, keep range instead */
+
+		case ZOOM_FRAME_MODE_KEEP_RANGE:
+		default:
+			newrct.xmax = scene->r.cfra + (w / 2);
+			newrct.xmin = scene->r.cfra - (w / 2);
+			newrct.ymax = ar->v2d.cur.ymax;
+			newrct.ymin = ar->v2d.cur.ymin;
+			break;
+	}
+
+	UI_view2d_smooth_view(C, ar, &newrct, smooth_viewtx);
+}
 /* *************************************************** */
diff --git a/source/blender/editors/include/ED_anim_api.h b/source/blender/editors/include/ED_anim_api.h
index 73f28986375..0f70bf3c745 100644
--- a/source/blender/editors/include/ED_anim_api.h
+++ b/source/blender/editors/include/ED_anim_api.h
@@ -659,6 +659,7 @@ void ANIM_list_elem_update(struct Scene *scene, bAnimListElem *ale);
 /* data -> channels syncing */
 void ANIM_sync_animchannels_to_data(const struct bContext *C);
 
+void ANIM_center_frame(struct bContext *C, int smooth_viewtx);
 /* ************************************************* */
 /* OPERATORS */
 	
diff --git a/source/blender/editors/include/UI_view2d.h b/source/blender/editors/include/UI_view2d.h
index 430093b641b..2c8f5f6590a 100644
--- a/source/blender/editors/include/UI_view2d.h
+++ b/source/blender/editors/include/UI_view2d.h
@@ -233,7 +233,6 @@ void ED_keymap_view2d(struct wmKeyConfig *keyconf);
 
 void UI_view2d_smooth_view(struct bContext *C, struct ARegion *ar,
                            const struct rctf *cur, const int smooth_viewtx);
-void UI_view2d_center_frame(struct bContext *C, int smooth_viewtx);
 #define UI_MARKER_MARGIN_Y (42 * UI_DPI_FAC)
 
 #endif /* __UI_VIEW2D_H__ */
diff --git a/source/blender/editors/interface/view2d_ops.c b/source/blender/editors/interface/view2d_ops.c
index 9fed02ee096..eafc5c1d24c 100644
--- a/source/blender/editors/interface/view2d_ops.c
+++ b/source/blender/editors/interface/view2d_ops.c
@@ -1468,21 +1468,6 @@ void UI_view2d_smooth_view(
 	}
 }
 
-void UI_view2d_center_frame(struct bContext *C, int smooth_viewtx)
-{
-	ARegion *ar = CTX_wm_region(C);
-	Scene *scene = CTX_data_scene(C);
-	float w = BLI_rctf_size_x(&ar->v2d.cur);
-	rctf newrct;
-
-	newrct.xmax = scene->r.cfra + (w / 2);
-	newrct.xmin = scene->r.cfra - (w / 2);
-	newrct.ymax = ar->v2d.cur.ymax;
-	newrct.ymin = ar->v2d.cur.ymin;
-
-	UI_view2d_smooth_view(C, ar, &newrct, smooth_viewtx);
-}
-
 /* only meant for timer usage */
 static int view2d_smoothview_invoke(bContext *C, wmOperator *UNUSED(op), const wmEvent *event)
 {
diff --git a/source/blender/editors/space_action/action_edit.c b/source/blender/editors/space_action/action_edit.c
index debe3cb9730..90c38426164 100644
--- a/source/blender/editors/space_action/action_edit.c
+++ b/source/blender/editors/space_action/action_edit.c
@@ -429,7 +429,7 @@ static int actkeys_viewsel_exec(bContext *C, wmOperator *UNUSED(op))
 static int actkeys_view_frame_exec(bContext *C, wmOperator *op)
 {
 	const int smooth_viewtx = WM_operator_smooth_viewtx_get(op);
-	UI_view2d_center_frame(C, smooth_viewtx);
+	ANIM_center_frame(C, smooth_viewtx);
 
 	return OPERATOR_FINISHED;
 }
diff --git a/source/blender/editors/space_graph/graph_edit.c b/source/blender/editors/space_graph/graph_edit.c
index d450335d16a..a8cb4ce56ea 100644
--- a/source/blender/editors/space_graph/graph_edit.c
+++ b/source/blender/editors/space_graph/graph_edit.c
@@ -261,7 +261,7 @@ static int graphkeys_view_selected_exec(bContext *C, wmOperator *op)
 static int graphkeys_view_frame_exec(bContext *C, wmOperator *op)
 {
 	const int smooth_viewtx = WM_operator_smooth_viewtx_get(op);
-	UI_view2d_center_frame(C, smooth_viewtx);
+	ANIM_center_frame(C, smooth_viewtx);
 	return OPERATOR_FINISHED;
 }