Animation: allow manually setting the intended playback range for actions.

Some operations, e.g. adding a new action strip to NLA, require
knowing the active frame range of an action. However, currently it
can only be deduced by scanning the keyframes of the curves within
it. This is not ideal if e.g. curves are staggered for overlap.

As suggested by Nathan Vegdahl in comments to T54724, this patch adds
Action properties that allow manually specifying its active frame range.
The settings are exposed via a panel in the Dopesheet and Action Editor.
When enabled, the range is highlighted in the background using a striped
fill to distinguish it from the solid filled regular playback range.

When set, the frame range is used when adding or updating NLA tracks,
and by add-ons using `Action.frame_range`, e.g. FBX exporter.

Differential Revision: https://developer.blender.org/D11803

1 files changed, 68 insertions, 0 deletions

diff --git a/source/blender/editors/animation/anim_draw.c b/source/blender/editors/animation/anim_draw.c
index 993d10cf303..f5a5609aa2e 100644
--- a/source/blender/editors/animation/anim_draw.c
+++ b/source/blender/editors/animation/anim_draw.c
@@ -168,6 +168,74 @@ void ANIM_draw_framerange(Scene *scene, View2D *v2d)
   immUnbindProgram();
 }
 
+/**
+ * Draw manually set intended playback frame range guides for the action in the background.
+ * Allows specifying a subset of the Y range of the view.
+ */
+void ANIM_draw_action_framerange(
+    AnimData *adt, bAction *action, View2D *v2d, float ymin, float ymax)
+{
+  if ((action->flag & ACT_FRAME_RANGE) == 0) {
+    return;
+  }
+
+  /* Compute the dimensions. */
+  CLAMP_MIN(ymin, v2d->cur.ymin);
+  CLAMP_MAX(ymax, v2d->cur.ymax);
+
+  if (ymin > ymax) {
+    return;
+  }
+
+  const float sfra = BKE_nla_tweakedit_remap(adt, action->frame_start, NLATIME_CONVERT_MAP);
+  const float efra = BKE_nla_tweakedit_remap(adt, action->frame_end, NLATIME_CONVERT_MAP);
+
+  /* Diagonal stripe filled area outside of the frame range. */
+  GPU_blend(GPU_BLEND_ALPHA);
+
+  GPUVertFormat *format = immVertexFormat();
+  uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
+
+  immBindBuiltinProgram(GPU_SHADER_2D_DIAG_STRIPES);
+
+  float color[4];
+  UI_GetThemeColorShadeAlpha4fv(TH_BACK, -40, -50, color);
+
+  immUniform4f("color1", color[0], color[1], color[2], color[3]);
+  immUniform4f("color2", 0.0f, 0.0f, 0.0f, 0.0f);
+  immUniform1i("size1", 2 * U.dpi_fac);
+  immUniform1i("size2", 4 * U.dpi_fac);
+
+  if (sfra < efra) {
+    immRectf(pos, v2d->cur.xmin, ymin, sfra, ymax);
+    immRectf(pos, efra, ymin, v2d->cur.xmax, ymax);
+  }
+  else {
+    immRectf(pos, v2d->cur.xmin, ymin, v2d->cur.xmax, ymax);
+  }
+
+  immUnbindProgram();
+
+  GPU_blend(GPU_BLEND_NONE);
+
+  /* Thin lines where the actual frames are. */
+  immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+  immUniformThemeColorShade(TH_BACK, -60);
+
+  GPU_line_width(1.0f);
+
+  immBegin(GPU_PRIM_LINES, 4);
+
+  immVertex2f(pos, sfra, ymin);
+  immVertex2f(pos, sfra, ymax);
+
+  immVertex2f(pos, efra, ymin);
+  immVertex2f(pos, efra, ymax);
+
+  immEnd();
+  immUnbindProgram();
+}
+
 /* *************************************************** */
 /* NLA-MAPPING UTILITIES (required for drawing and also editing keyframes). */