UI: Remove fractional scaling ifdefs

Among the systems we officially support, the oldest Qt version is Qt 5.9
on Ubuntu 18.04. Fractional scaling is supported in Qt 5.6 and newer. We
should be able to safely remove these ifdefs.

UI/display-helpers.hpp

@@ -17,10 +17,6 @@
 
 #pragma once
 
-#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
-#define SUPPORTS_FRACTIONAL_SCALING
-#endif
-
 static inline void GetScaleAndCenterPos(int baseCX, int baseCY, int windowCX,
 					int windowCY, int &x, int &y,
 					float &scale)
@@ -55,9 +51,5 @@ static inline void GetCenterPosFromFixedScale(int baseCX, int baseCY,
 
 static inline QSize GetPixelSize(QWidget *widget)
 {
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	return widget->size() * widget->devicePixelRatioF();
-#else
-	return widget->size() * widget->devicePixelRatio();
-#endif
 }

UI/window-basic-interaction.cpp

@@ -221,11 +221,7 @@ static int TranslateQtMouseEventModifiers(QMouseEvent *event)
 bool OBSBasicInteraction::GetSourceRelativeXY(int mouseX, int mouseY, int &relX,
 					      int &relY)
 {
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	float pixelRatio = devicePixelRatioF();
-#else
-	float pixelRatio = devicePixelRatio();
-#endif
 	int mouseXscaled = (int)roundf(mouseX * pixelRatio);
 	int mouseYscaled = (int)roundf(mouseY * pixelRatio);
 

UI/window-basic-main.cpp

@@ -1279,13 +1279,8 @@ bool OBSBasic::InitBasicConfigDefaults()
 	uint32_t cx = primaryScreen->size().width();
 	uint32_t cy = primaryScreen->size().height();
 
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	cx *= devicePixelRatioF();
 	cy *= devicePixelRatioF();
-#elif
-	cx *= devicePixelRatio();
-	cy *= devicePixelRatio();
-#endif
 
 	bool oldResolutionDefaults = config_get_bool(
 		App()->GlobalConfig(), "General", "Pre19Defaults");

UI/window-basic-preview.cpp

@@ -13,9 +13,6 @@
 
 #define HANDLE_RADIUS 4.0f
 #define HANDLE_SEL_RADIUS (HANDLE_RADIUS * 1.5f)
-#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
-#define SUPPORTS_FRACTIONAL_SCALING
-#endif
 
 /* TODO: make C++ math classes and clean up code here later */
 
@@ -44,11 +41,7 @@ OBSBasicPreview::~OBSBasicPreview()
 vec2 OBSBasicPreview::GetMouseEventPos(QMouseEvent *event)
 {
 	OBSBasic *main = reinterpret_cast<OBSBasic *>(App()->GetMainWindow());
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	float pixelRatio = main->devicePixelRatioF();
-#else
-	float pixelRatio = main->devicePixelRatio();
-#endif
 	float scale = pixelRatio / main->previewScale;
 	vec2 pos;
 	vec2_set(&pos,
@@ -406,11 +399,7 @@ void OBSBasicPreview::GetStretchHandleData(const vec2 &pos, bool ignoreGroup)
 	if (!scene)
 		return;
 
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	float scale = main->previewScale / main->devicePixelRatioF();
-#else
-	float scale = main->previewScale / main->devicePixelRatio();
-#endif
 	vec2 scaled_pos = pos;
 	vec2_divf(&scaled_pos, &scaled_pos, scale);
 	HandleFindData data(scaled_pos, scale);
@@ -533,11 +522,7 @@ void OBSBasicPreview::mousePressEvent(QMouseEvent *event)
 	}
 
 	OBSBasic *main = reinterpret_cast<OBSBasic *>(App()->GetMainWindow());
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 	float pixelRatio = main->devicePixelRatioF();
-#else
-	float pixelRatio = main->devicePixelRatio();
-#endif
 	float x = float(event->x()) - main->previewX / pixelRatio;
 	float y = float(event->y()) - main->previewY / pixelRatio;
 	Qt::KeyboardModifiers modifiers = QGuiApplication::keyboardModifiers();
@@ -1552,11 +1537,7 @@ void OBSBasicPreview::mouseMoveEvent(QMouseEvent *event)
 			mousePos = pos;
 			OBSBasic *main = reinterpret_cast<OBSBasic *>(
 				App()->GetMainWindow());
-#ifdef SUPPORTS_FRACTIONAL_SCALING
 			float scale = main->devicePixelRatioF();
-#else
-			float scale = main->devicePixelRatio();
-#endif
 			float x = float(event->x()) - main->previewX / scale;
 			float y = float(event->y()) - main->previewY / scale;
 			vec2_set(&startPos, x, y);