Lots of hidpi fixes (tested on Debian/XFCE under X11 so far)

Author: azonenberg

src/ngscopeclient/FontManager.h

@@ -1,8 +1,8 @@
 /***********************************************************************************************************************
 *                                                                                                                      *
-* glscopeclient                                                                                                        *
+* ngscopeclient                                                                                                        *
 *                                                                                                                      *
-* Copyright (c) 2012-2022 Andrew D. Zonenberg                                                                          *
+* Copyright (c) 2012-2025 Andrew D. Zonenberg                                                                          *
 * All rights reserved.                                                                                                 *
 *                                                                                                                      *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the     *

src/ngscopeclient/MainWindow.h

@@ -546,9 +546,17 @@ class MainWindow : public VulkanWindow
 	FontWithSize GetFontPref(const std::string& name)
 	{
 		auto desc = m_session.GetPreferences().GetFont(name.c_str());
-		return std::pair<ImFont*, float>(m_fontmgr.GetFont(desc), desc.second);
+		return std::pair<ImFont*, float>(m_fontmgr.GetFont(desc), desc.second * GetFontScale());
 	}
 
+	/**
+		@brief Get scaling factor for fonts being drawn with ImDrawList
+
+		For now, normalize everything to a nominal size 13 default font
+	 */
+	float GetFontScale()
+	{ return ImGui::GetFontSize() / 13; }
+
 	ImU32 GetColorPref(const std::string& name)
 	{ return m_session.GetPreferences().GetColor(name); }
 

src/ngscopeclient/VulkanWindow.cpp

@@ -181,16 +181,20 @@ VulkanWindow::VulkanWindow(const string& title, shared_ptr<QueueHandle> queue)
 		ImGui_ImplVulkan_Init(&info);
 	}
 
-	// Apply DPI scaling now that glfw initialized
+	//Apply DPI scaling now that glfw initialized
+	//This appears to be cached by glfw at init time and is not updated for dynamic scaling changes at least on X11
+	//TODO: can we fix this by moving to SDL?
 	float scale = GetContentScale();
-
-	LogTrace("Applying ImGui style scale factor: %.2f\n", scale);
+	LogTrace("Using ImGui style scale factor: %.2f\n", scale);
 
 	//WORKAROUND: handle HiDPI correctly on macOS.
+	//This is probably wrong, per comment in imgui_impl_glfw "Apple platforms use FramebufferScale"
 #ifdef __APPLE__
 	io.FontGlobalScale = 1.0f / scale;
 #else
-	ImGui::GetStyle().ScaleAllSizes(scale);
+	//ImGui::GetStyle().ScaleAllSizes(scale);
+	//ImGui::GetStyle().FontScaleMain = scale;
+	//Don't change any scaling for now in hidpi mode!
 #endif
 
 	//Hook a couple of backend functions with mutexing

src/ngscopeclient/WaveformArea.cpp

@@ -1677,7 +1677,7 @@ void WaveformArea::RenderProtocolWaveform(std::shared_ptr<DisplayedChannel> chan
 	if(ifirst > 0)
 		ifirst --;
 
-	float ybot = (channel->GetYButtonPos() * ImGui::GetWindowDpiScale()) + start.y;
+	float ybot = channel->GetYButtonPos() + start.y;
 	float ytop = ybot - m_channelButtonHeight;
 	float ymid = ybot - m_channelButtonHeight/2;
 
@@ -4076,7 +4076,7 @@ void WaveformArea::OnDragUpdate()
 	{
 		case DRAG_STATE_Y_AXIS:
 			{
-				float dy = ImGui::GetIO().MouseDelta.y * ImGui::GetWindowDpiScale();
+				float dy = ImGui::GetIO().MouseDelta.y;
 				m_yAxisOffset -= PixelsToYAxisUnits(dy);
 
 				for(auto chan : m_displayedChannels)

src/ngscopeclient/WaveformGroup.cpp

@@ -938,7 +938,7 @@ void WaveformGroup::RenderTimeline(float width, float height)
 	if(m_dragState == DRAG_STATE_TIMELINE)
 	{
 		//Use relative delta, not drag delta, since we update the offset every frame
-		float dx = mouseDelta.x * ImGui::GetWindowDpiScale();
+		float dx = mouseDelta.x;
 		if(dx != 0)
 		{
 			m_xAxisOffset -= PixelsToXAxisUnits(dx);
@@ -950,10 +950,9 @@ void WaveformGroup::RenderTimeline(float width, float height)
 	}
 
 	//Dimensions for various things
-	float dpiScale = ImGui::GetWindowDpiScale();
-	float fineTickLength = 10 * dpiScale;
+	float fineTickLength = 10;
 	float coarseTickLength = height;
-	const double min_label_grad_width = 75 * dpiScale;	//Minimum distance between text labels
+	const double min_label_grad_width = 6 * ImGui::GetFontSize();	//Minimum distance between text labels
 	float thickLineWidth = 2;
 	float thinLineWidth = 1;
 	float ymid = pos.y + height/2;

src/ngscopeclient/WaveformGroup.h

@@ -2,7 +2,7 @@
 *                                                                                                                      *
 * ngscopeclient                                                                                                        *
 *                                                                                                                      *
-* Copyright (c) 2012-2024 Andrew D. Zonenberg and contributors                                                         *
+* Copyright (c) 2012-2025 Andrew D. Zonenberg and contributors                                                         *
 * All rights reserved.                                                                                                 *
 *                                                                                                                      *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the     *
@@ -117,7 +117,7 @@ class WaveformGroup
 	void ClearPersistence();
 
 	float GetYAxisWidth()
-	{ return 6 * ImGui::GetFontSize() * ImGui::GetWindowDpiScale(); }
+	{ return 6 * ImGui::GetFontSize(); }
 
 	float GetSpacing()
 	{ return ImGui::GetFrameHeightWithSpacing() - ImGui::GetFrameHeight(); }