CVideo: remove get_dpi and get_dpi_scale_factor.

screen_pitch_microns is deprecated, and has been removed from the
GUI_SCALE_RESOLUTION macro in WML. The macro itself has been left in
place for potential future use.

The screen_pitch_microns variable has been left in place, but is now
a constant and will only ever return the default value equivalent to
96 DPI.

data/campaigns/World_Conquest/gui/help_dialog.cfg

@@ -4,7 +4,7 @@
 {gui/macros}
 
 #define FORMULA_GUI_SCALE_RESOLUTION SIZE
-    "(max({SIZE}, floor({SIZE} * 265 * 2 / (3 * screen_pitch_microns))))"
+    "({SIZE})"
 #enddef
 
 [resolution]

data/gui/macros/_initial.cfg

@@ -373,14 +373,11 @@
 	window_height = 900
 #enddef
 
-# The magic number 265 in the below formula is the pixel pitch in microns
-# corresponding to 96 dpi, which the old layout seems to have been based on.
-# The extra factor of 2/3 in the formula is a fudge factor based on the guess
-# that the old fonts took up approximately 1.5 pixels per point size at 96
-# dpi. It came out looking pretty decent on my 90-micron monitor.
+# scaling based on physical DPI has been disabled. This macro remains,
+# and may still be used in the future for adaptive or manual UI scaling.
 
 #define GUI_SCALE_RESOLUTION SIZE
-	(max({SIZE}, floor({SIZE} * 265 * 2 / (3 * screen_pitch_microns))))
+	({SIZE})
 #enddef
 
 #define GUI_WINDOW_PERC_FIXED_SIZE_CENTERED PERC_W PERC_H WIDTH HEIGHT

src/build_info.cpp

@@ -568,17 +568,6 @@ list_formatter video_settings_report_internal(const std::string& heading = "")
 	const auto& current_driver = CVideo::current_driver();
 	auto drivers = CVideo::enumerate_drivers();
 
-	const auto& dpi = video.get_dpi();
-	const auto& scale = video.get_dpi_scale_factor();
-	std::string dpi_report, scale_report;
-
-	if(dpi.first == 0.0f || dpi.second == 0.0f) {
-		scale_report = dpi_report = "<unknown>";
-	} else {
-		dpi_report = geometry_to_string(dpi.first, dpi.second);
-		scale_report = geometry_to_string(scale.first, scale.second);
-	}
-
 	fmt.insert("SDL video drivers", format_sdl_driver_list(drivers, current_driver));
 	fmt.insert("Window size", geometry_to_string(
 		video.current_resolution().x, video.current_resolution().y));
@@ -587,8 +576,6 @@ list_formatter video_settings_report_internal(const std::string& heading = "")
 	fmt.insert("Final render target size", geometry_to_string(
 		video.output_size().x, video.output_size().y));
 	fmt.insert("Screen refresh rate", std::to_string(video.current_refresh_rate()));
-	fmt.insert("Screen dots per inch", dpi_report);
-	fmt.insert("Screen dpi scale factor", scale_report);
 
 	return fmt;
 }

src/draw.cpp

@@ -302,6 +302,7 @@ void draw::tiled(const texture& tex, const SDL_Rect& dst, bool centered,
 /* RAII state manipulation */
 /***************************/
 
+
 draw::clip_setter::clip_setter(const SDL_Rect& clip)
 	: c_()
 {

src/gui/widgets/settings.cpp

@@ -17,9 +17,6 @@
 
 #include "display.hpp"
 
-#define MAGIC_DPI_MATCH_VIDEO 96
-#define MICRONS_PER_INCH 25400
-
 namespace gui2
 {
 bool new_widgets = false;
@@ -28,7 +25,14 @@ namespace settings
 {
 unsigned screen_width = 0;
 unsigned screen_height = 0;
-unsigned screen_pitch_microns = MICRONS_PER_INCH / MAGIC_DPI_MATCH_VIDEO;
+/** screen_pitch_microns is deprecated. Do not use it.
+ *
+ * This value corresponds to a physical DPI of 96. But physical DPI should
+ * not be used to make rendering decisions. With the ability to set pixel
+ * scale, it can be assumed that one pixel in draw-space is neither too
+ * small nor too large.
+ */
+const unsigned screen_pitch_microns = 265;
 unsigned gamemap_x_offset = 0;
 
 unsigned gamemap_width = 0;
@@ -57,13 +61,6 @@ void update_screen_size_variables()
 	screen_width = rect.w;
 	screen_height = rect.h;
 
-	// TODO: highdpi - remove usage
-	// Use of screen_pitch_microns should probably be deprecated, as physical
-	// DPI is not an accurate method of determining perceptual pixel size.
-	//auto [scalew, scaleh] = video.get_dpi_scale_factor();
-	//float avgscale = (scalew + scaleh)/2;
-	//screen_pitch_microns = MICRONS_PER_INCH / (avgscale * MAGIC_DPI_MATCH_VIDEO);
-
 	gamemap_width = screen_width;
 	gamemap_height = screen_height;
 

src/gui/widgets/settings.hpp

@@ -44,7 +44,7 @@ namespace settings
  */
 extern unsigned screen_width;
 extern unsigned screen_height;
-extern unsigned screen_pitch_microns; /* Pixel pitch in microns */
+extern const unsigned screen_pitch_microns; /* Deprecated, do not use */
 
 /**
  * The offset between the left edge of the screen and the gamemap.

src/video.cpp

@@ -738,44 +738,6 @@ bool CVideo::window_has_flags(uint32_t flags) const
 	return (window->get_flags() & flags) != 0;
 }
 
-std::pair<float, float> CVideo::get_dpi() const
-{
-	float hdpi, vdpi;
-	if(window && SDL_GetDisplayDPI(window->get_display_index(), nullptr, &hdpi, &vdpi) == 0) {
-#ifdef TARGET_OS_OSX
-		// SDL 2.0.12 changes SDL_GetDisplayDPI. Function now returns DPI
-		// multiplied by screen's scale factor. This part of code reverts
-		// this multiplication.
-		//
-		// For more info see issue: https://github.com/wesnoth/wesnoth/issues/5019
-
-		if(sdl_get_version() >= version_info{2, 0, 12}) {
-			float scale_factor = desktop::apple::get_scale_factor(window->get_display_index());
-			hdpi /= scale_factor;
-			vdpi /= scale_factor;
-		}
-#endif
-		return { hdpi, vdpi };
-	}
-	// SDL doesn't know the screen dpi, there's a configuration issue, or we
-	// don't have a window yet.
-	return { 0.0f, 0.0f };
-}
-
-std::pair<float, float> CVideo::get_dpi_scale_factor() const
-{
-	auto dpi = get_dpi();
-	if(dpi.first != 0.0f && dpi.second != 0.0f) {
-		// adjust for pixel scale
-		SDL_Point wsize = window_size();
-		dpi.first *= float(get_width()) / wsize.x;
-		dpi.second *= float(get_height()) / wsize.y;
-		return { dpi.first / MAGIC_DPI_SCALE_NUMBER, dpi.second / MAGIC_DPI_SCALE_NUMBER };
-	}
-	// Assume a scale factor of 1.0 if the screen dpi is currently unknown.
-	return { 1.0f, 1.0f };
-}
-
 std::vector<point> CVideo::get_available_resolutions(const bool include_current)
 {
 	std::vector<point> result;

src/video.hpp

@@ -196,12 +196,6 @@ public:
 	 */
 	int get_pixel_scale() const { return pixel_scale_; }
 
-	/** The current game screen dpi. */
-	std::pair<float, float> get_dpi() const;
-
-	/** The current scale factor on High-DPI screens. */
-	std::pair<float, float> get_dpi_scale_factor() const;
-
 	/**
 	 * Clip a rectangle to the drawing area.
 	 *