Support mouse wheel

MainWindow.cpp

@@ -389,6 +389,19 @@ void MainWindow::reconfigure() noexcept {
     _renderer.resize(buffer_size());
 }
 
+void MainWindow::scroll(MouseWheelAxis axis, float distance) noexcept {
+    switch (axis) {
+    case MouseWheelAxis::Vertical:
+        ImGui::GetIO().AddMouseWheelEvent(0, -distance);
+        break;
+    case MouseWheelAxis::Horizontal:
+        ImGui::GetIO().AddMouseWheelEvent(-distance, 0);
+        break;
+    default:
+        break;
+    }
+}
+
 void MainWindow::text(const std::string& str) const noexcept {
     ImGui::GetIO().AddInputCharactersUTF8(str.c_str());
 }

MainWindow.hpp

@@ -13,6 +13,7 @@ class MainWindow final : public Window {
     virtual void pointer_click(uint32_t button, wl_pointer_button_state state) noexcept override;
     virtual void pointer_motion(float x, float y) noexcept override;
     virtual void reconfigure() noexcept override;
+    virtual void scroll(MouseWheelAxis axis, float distance) noexcept override;
     virtual void text(const std::string& str) const noexcept override;
 
     void render();

wayland/MouseWheelAxis.hpp

@@ -0,0 +1,6 @@
+#pragma once
+
+enum class MouseWheelAxis {
+    Vertical,
+    Horizontal    
+};

wayland/Pointer.cpp

@@ -40,7 +40,19 @@ Pointer::Pointer(Seat& seat)
                 self._focus->pointer_click(button, static_cast<wl_pointer_button_state>(state));
             }
         },
-        .axis = [](void *, wl_pointer *, uint32_t, uint32_t, wl_fixed_t) noexcept {},
+        .axis = [](void * data, wl_pointer *, uint32_t, uint32_t axis, wl_fixed_t value) noexcept {
+            auto& self = *static_cast<Pointer *>(data);
+            if (self._focus) {
+                const auto distance = static_cast<float>(wl_fixed_to_double(value));
+                switch (axis) {
+                case WL_POINTER_AXIS_VERTICAL_SCROLL:
+                    self._focus->scroll(MouseWheelAxis::Vertical, distance);
+                    break;
+                case WL_POINTER_AXIS_HORIZONTAL_SCROLL:
+                    self._focus->scroll(MouseWheelAxis::Horizontal, distance);
+                }
+            }
+        },
         .frame = [](void *, wl_pointer *) noexcept {},
         .axis_source = [](void *, wl_pointer *, uint32_t) noexcept {},
         .axis_stop = [](void *, wl_pointer *, uint32_t, uint32_t) noexcept {},

wayland/Window.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "MouseWheelAxis.hpp"
 #include "WaylandPointer.hpp"
 #include "cursor/CursorBase.hpp"
 
@@ -25,6 +26,7 @@ class Window {
     virtual void pointer_click(uint32_t button, wl_pointer_button_state state) noexcept = 0;
     virtual void pointer_motion(float x, float y) noexcept = 0;
     virtual void reconfigure() noexcept = 0;
+    virtual void scroll(MouseWheelAxis axis, float distance) noexcept = 0;
     virtual void text(const std::string& str) const noexcept = 0;
 
     void register_cursor(CursorBase *cursor);