Make the scroll amount configurable (#380)

* Make the scroll amount configurable

* change default scroll amount to 100

Author: davidmartos96

application.go

@@ -327,7 +327,10 @@ func (a *Application) Run() error {
 	a.window.SetCursorEnterCallback(windowManager.glfwCursorEnterCallback)
 	a.window.SetCursorPosCallback(windowManager.glfwCursorPosCallback)
 	a.window.SetMouseButtonCallback(windowManager.glfwMouseButtonCallback)
-	a.window.SetScrollCallback(windowManager.glfwScrollCallback)
+	a.window.SetScrollCallback(
+		func(window *glfw.Window, xoff float64, yoff float64) {
+			windowManager.glfwScrollCallback(window, xoff, yoff, a.config.scrollAmount)
+		})
 
 	// Shutdown the engine if we return from this function (on purpose or panic)
 	defer a.engine.Shutdown()

glfw.go

@@ -188,8 +188,8 @@ func (m *windowManager) glfwMouseButtonCallback(window *glfw.Window, key glfw.Mo
 	}
 }
 
-func (m *windowManager) glfwScrollCallback(window *glfw.Window, xoff float64, yoff float64) {
-	const scrollModifier = -50
+func (m *windowManager) glfwScrollCallback(window *glfw.Window, xoff float64, yoff float64, scrollAmount float64) {
+	scrollModifier := -scrollAmount
 	m.sendPointerEventScroll(window, xoff*scrollModifier, yoff*scrollModifier)
 }
 

option.go

@@ -22,6 +22,7 @@ type config struct {
 
 	forcePixelRatio float64
 	keyboardLayout  KeyboardShortcuts
+	scrollAmount    float64
 
 	plugins []Plugin
 }
@@ -53,6 +54,7 @@ var defaultApplicationConfig = config{
 	keyboardLayout:    KeyboardQwertyLayout,
 	windowMode:        WindowModeDefault,
 	windowAlwaysOnTop: false,
+	scrollAmount:      100.0,
 }
 
 // Option for Application
@@ -226,3 +228,10 @@ func VirtualKeyboardHide(hideCallback func()) Option {
 		defaultTextinputPlugin.virtualKeyboardHide = hideCallback
 	}
 }
+
+// ScrollAmount sets the number of pixels to scroll with the mouse wheel
+func ScrollAmount(amount float64) Option {
+	return func(c *config) {
+		c.scrollAmount = amount
+	}
+}