Route animation timeline scrubbing through app core

src/app_core/document_animation.h

@@ -3,6 +3,7 @@
 #include "foundation/result.h"
 
 #include <algorithm>
+#include <cmath>
 #include <cstdint>
 #include <limits>
 
@@ -70,6 +71,15 @@ struct DocumentAnimationOnionFrameRange {
     int last_frame = 0;
 };
 
+inline constexpr float document_animation_timeline_frame_width = 35.0F;
+
+struct DocumentAnimationTimelineScrubPlan {
+    int total_duration = 1;
+    float cursor_x = 0.0F;
+    float frame_width = document_animation_timeline_frame_width;
+    int target_frame = 0;
+};
+
 class DocumentAnimationServices {
 public:
     virtual ~DocumentAnimationServices() = default;
@@ -162,6 +172,37 @@ public:
         });
 }
 
+[[nodiscard]] inline pp::foundation::Result<DocumentAnimationTimelineScrubPlan> plan_animation_timeline_scrub(
+    int total_duration,
+    float cursor_x,
+    float frame_width = document_animation_timeline_frame_width)
+{
+    if (total_duration <= 0) {
+        return pp::foundation::Result<DocumentAnimationTimelineScrubPlan>::failure(
+            pp::foundation::Status::invalid_argument("animation timeline duration must be greater than zero"));
+    }
+
+    if (!std::isfinite(cursor_x)) {
+        return pp::foundation::Result<DocumentAnimationTimelineScrubPlan>::failure(
+            pp::foundation::Status::invalid_argument("animation timeline cursor position must be finite"));
+    }
+
+    if (!std::isfinite(frame_width) || frame_width <= 0.0F) {
+        return pp::foundation::Result<DocumentAnimationTimelineScrubPlan>::failure(
+            pp::foundation::Status::invalid_argument("animation timeline frame width must be positive and finite"));
+    }
+
+    const auto raw_frame = static_cast<std::int64_t>(std::floor(cursor_x / frame_width));
+    const auto target_frame = std::clamp<std::int64_t>(raw_frame, 0, total_duration - 1);
+    return pp::foundation::Result<DocumentAnimationTimelineScrubPlan>::success(
+        DocumentAnimationTimelineScrubPlan {
+            .total_duration = total_duration,
+            .cursor_x = cursor_x,
+            .frame_width = frame_width,
+            .target_frame = static_cast<int>(target_frame),
+        });
+}
+
 [[nodiscard]] inline float animation_onion_frame_alpha(
     const DocumentAnimationOnionFrameRange& range,
     int frame) noexcept

src/node_panel_animation.cpp

@@ -347,10 +347,13 @@ kEventResult NodeAnimationTimeline::handle_event(Event* e)
     parent::handle_event(e);
     static int signaled_frame = -1;
     auto me = static_cast<MouseEvent*>(e);
-    auto ge = static_cast<GestureEvent*>(e);
     auto update = [&](){
         auto loc = me->m_pos - m_pos;
-        m_frame = glm::clamp((int)glm::floor(loc.x / 35.f), 0, Canvas::I->anim_duration() - 1);
+        const int total_duration = Canvas::I ? Canvas::I->anim_duration() : 0;
+        const auto scrub = pp::app::plan_animation_timeline_scrub(total_duration, loc.x);
+        if (!scrub)
+            return;
+        m_frame = scrub.value().target_frame;
         if (on_frame_changed && signaled_frame != m_frame)
             on_frame_changed(this, m_frame);
         signaled_frame = m_frame;