Route quick slider preview through app core

src/app_core/quick_ui.h

@@ -2,6 +2,8 @@
 
 #include "foundation/result.h"
 
+#include <cmath>
+
 namespace pp::app {
 
 enum class QuickUiSlotKind {
@@ -35,6 +37,27 @@ struct QuickUiPlan {
     bool mutates_quick_state = false;
 };
 
+struct QuickSliderPreviewInput {
+    bool ui_rtl = false;
+    float slider_x = 0.0F;
+    float slider_y = 0.0F;
+    float slider_height = 0.0F;
+    float zoom = 1.0F;
+    bool has_pen_mode = false;
+    bool has_line_mode = false;
+};
+
+struct QuickSliderPreviewPlan {
+    float cursor_x = 0.0F;
+    float cursor_y = 0.0F;
+    bool updates_pen_mode = false;
+    bool updates_line_mode = false;
+    bool draws_tip = false;
+    bool disables_pen_outline = false;
+    bool redraws_brush_preview = false;
+    bool invokes_change_callback = false;
+};
+
 class QuickUiServices {
 public:
     virtual ~QuickUiServices() = default;
@@ -45,6 +68,15 @@ public:
     virtual void reset_state(bool fire_event) = 0;
 };
 
+[[nodiscard]] inline pp::foundation::Status validate_quick_slider_float(float value) noexcept
+{
+    if (!std::isfinite(value)) {
+        return pp::foundation::Status::invalid_argument("quick slider preview value must be finite");
+    }
+
+    return pp::foundation::Status::success();
+}
+
 [[nodiscard]] inline pp::foundation::Status validate_quick_slot_count(int slot_count) noexcept
 {
     if (slot_count <= 0) {
@@ -68,6 +100,47 @@ public:
     return pp::foundation::Status::success();
 }
 
+[[nodiscard]] inline pp::foundation::Result<QuickSliderPreviewPlan> plan_quick_slider_preview(
+    const QuickSliderPreviewInput& input)
+{
+    const auto x_status = validate_quick_slider_float(input.slider_x);
+    if (!x_status.ok()) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(x_status);
+    }
+    const auto y_status = validate_quick_slider_float(input.slider_y);
+    if (!y_status.ok()) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(y_status);
+    }
+    const auto height_status = validate_quick_slider_float(input.slider_height);
+    if (!height_status.ok()) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(height_status);
+    }
+    if (input.slider_height < 0.0F) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(
+            pp::foundation::Status::invalid_argument("quick slider preview height must not be negative"));
+    }
+    const auto zoom_status = validate_quick_slider_float(input.zoom);
+    if (!zoom_status.ok()) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(zoom_status);
+    }
+    if (input.zoom <= 0.0F) {
+        return pp::foundation::Result<QuickSliderPreviewPlan>::failure(
+            pp::foundation::Status::invalid_argument("quick slider preview zoom must be positive"));
+    }
+
+    const float offset = input.ui_rtl ? -100.0F : 100.0F;
+    QuickSliderPreviewPlan plan;
+    plan.cursor_x = (input.slider_x + offset) * input.zoom;
+    plan.cursor_y = (input.slider_y + input.slider_height * 0.5F) * input.zoom;
+    plan.updates_pen_mode = input.has_pen_mode;
+    plan.updates_line_mode = input.has_line_mode;
+    plan.draws_tip = input.has_pen_mode || input.has_line_mode;
+    plan.disables_pen_outline = input.has_pen_mode;
+    plan.redraws_brush_preview = true;
+    plan.invokes_change_callback = true;
+    return pp::foundation::Result<QuickSliderPreviewPlan>::success(plan);
+}
+
 [[nodiscard]] inline pp::foundation::Result<QuickUiPlan> plan_quick_slot_click(
     QuickUiSlotKind slot_kind,
     int current_index,