Codechange: Slider widget used different range for drawing vs setting.

Using the same range for setting means that no workaround for setting the extremes is necessary.

(cherry picked from commit dd41de8931)

src/widgets/slider.cpp

@@ -16,6 +16,7 @@
 
 #include "../safeguards.h"
 
+static const int SLIDER_WIDTH = 3;
 
 /**
  * Draw a volume slider widget with know at given value
@@ -24,8 +25,6 @@
  */
 void DrawVolumeSliderWidget(Rect r, byte value)
 {
-	static const int slider_width = 3;
-
 	/* Draw a wedge indicating low to high volume level. */
 	const int ha = (r.bottom - r.top) / 5;
 	int wx1 = r.left, wx2 = r.right;
@@ -40,7 +39,7 @@ void DrawVolumeSliderWidget(Rect r, byte value)
 	GfxDrawLine(wedge[0].x, wedge[0].y, wedge[1].x, wedge[1].y, shadow);
 
 	/* Draw a slider handle indicating current volume level. */
-	const int sw = ScaleGUITrad(slider_width);
+	const int sw = ScaleGUITrad(SLIDER_WIDTH);
 	if (_current_text_dir == TD_RTL) value = 127 - value;
 	const int x = r.left + (value * (r.right - r.left - sw) / 127);
 	DrawFrameRect(x, r.top, x + sw, r.bottom, COLOUR_GREY, FR_NONE);
@@ -55,12 +54,10 @@ void DrawVolumeSliderWidget(Rect r, byte value)
  */
 bool ClickVolumeSliderWidget(Rect r, Point pt, byte &value)
 {
-	byte new_vol = Clamp((pt.x - r.left) * 127 / (r.right - r.left), 0, 127);
+	const int sw = ScaleGUITrad(SLIDER_WIDTH);
+	byte new_vol = Clamp((pt.x - r.left - sw / 2) * 127 / (r.right - r.left - sw), 0, 127);
 	if (_current_text_dir == TD_RTL) new_vol = 127 - new_vol;
 
-	/* Clamp to make sure min and max are properly settable */
-	if (new_vol > 124) new_vol = 127;
-	if (new_vol < 3) new_vol = 0;
 	if (new_vol != value) {
 		value = new_vol;
 		return true;