steamcompmgr: Add support for cursor resize-based scaling

X11/XCursor is not good at dynamically changing the requested cursor theme size. Always request the largest and downsample it ourselves.

src/meson.build

@@ -1,5 +1,6 @@
 dep_xdamage = dependency('xdamage')
 dep_xcomposite = dependency('xcomposite')
+dep_xcursor = dependency('xcursor')
 dep_xrender = dependency('xrender')
 dep_xext = dependency('xext')
 dep_xfixes = dependency('xfixes')
@@ -134,7 +135,7 @@ endif
       dep_xxf86vm, dep_xres, glm_dep, drm_dep, wayland_server,
       xkbcommon, thread_dep, sdl_dep, wlroots_dep,
       vulkan_dep, liftoff_dep, dep_xtst, dep_xmu, cap_dep, epoll_dep, pipewire_dep, librt_dep,
-      stb_dep, displayinfo_dep, openvr_dep,
+      stb_dep, displayinfo_dep, openvr_dep, dep_xcursor,
     ],
     install: true,
   )

src/steamcompmgr.cpp

@@ -32,6 +32,7 @@
 #include "xwayland_ctx.hpp"
 #include <X11/X.h>
 #include <X11/Xlib.h>
+#include <X11/Xcursor/Xcursor.h>
 #include <X11/extensions/xfixeswire.h>
 #include <cstdint>
 #include <drm_mode.h>
@@ -87,6 +88,8 @@
 #include "log.hpp"
 #include "defer.hpp"
 
+static const int g_nBaseCursorScale = 36;
+
 #if HAVE_PIPEWIRE
 #include "pipewire.hpp"
 #endif
@@ -99,6 +102,7 @@
 #define STB_IMAGE_WRITE_IMPLEMENTATION
 #include <stb_image.h>
 #include <stb_image_write.h>
+#include <stb_image_resize.h>
 
 #define GPUVIS_TRACE_IMPLEMENTATION
 #include "gpuvis_trace_utils.h"
@@ -1825,29 +1829,11 @@ bool MouseCursor::setCursorImage(char *data, int w, int h, int hx, int hy)
 
 bool MouseCursor::setCursorImageByName(const char *name)
 {
-	int screen = DefaultScreen(m_ctx->dpy);
-
-	XColor fg;
-	fg.pixel = WhitePixel(m_ctx->dpy, screen);
-	XQueryColor(m_ctx->dpy, DefaultColormap(m_ctx->dpy, screen), &fg);
-
-	XColor bg;
-	bg.pixel = BlackPixel(m_ctx->dpy, screen);
-	XQueryColor(m_ctx->dpy, DefaultColormap(m_ctx->dpy, screen), &bg);
-
 	int index = XmuCursorNameToIndex(name);
 	if (index < 0)
 		return false;
 
-	Font font = XLoadFont(m_ctx->dpy, "cursor");
-	if (!font)
-		return false;
-	defer( XUnloadFont(m_ctx->dpy, font) );
-
-	Cursor cursor = XCreateGlyphCursor(m_ctx->dpy, font, font, index, index + 1, &fg, &bg);
-	if ( !cursor )
-		return false;
-	defer( XFreeCursor(m_ctx->dpy, cursor) );
+	Cursor cursor = XcursorShapeLoadCursor( m_ctx->dpy, index );
 
 	XDefineCursor(m_ctx->dpy, DefaultRootWindow(m_ctx->dpy), cursor);
 	XFlush(m_ctx->dpy);
@@ -1988,6 +1974,9 @@ bool MouseCursor::getTexture()
 	m_hotspotX = image->xhot;
 	m_hotspotY = image->yhot;
 
+	int nDesiredWidth, nDesiredHeight;
+	GetDesiredSize( nDesiredWidth, nDesiredHeight );
+
 	uint32_t surfaceWidth;
 	uint32_t surfaceHeight;
 	if ( BIsNested() == false && alwaysComposite == false )
@@ -1997,8 +1986,8 @@ bool MouseCursor::getTexture()
 	}
 	else
 	{
-		surfaceWidth = image->width;
-		surfaceHeight = image->height;
+		surfaceWidth = nDesiredWidth;
+		surfaceHeight = nDesiredHeight;
 	}
 
 	m_texture = nullptr;
@@ -2008,20 +1997,59 @@ bool MouseCursor::getTexture()
 
 	std::shared_ptr<std::vector<uint32_t>> cursorBuffer = nullptr;
 
+	int nContentWidth = image->width;
+	int nContentHeight = image->height;
+
 	if (image->width && image->height)
 	{
-		cursorBuffer = std::make_shared<std::vector<uint32_t>>(surfaceWidth * surfaceHeight);
-		for (int i = 0; i < image->height; i++) {
-			for (int j = 0; j < image->width; j++) {
-				(*cursorBuffer)[i * surfaceWidth + j] = image->pixels[i * image->width + j];
+		if ( nDesiredWidth < image->width || nDesiredHeight < image->height )
+		{
+			std::vector<uint32_t> pixels(image->width * image->height);
+			for (int i = 0; i < image->height; i++)
+			{
+				for (int j = 0; j < image->width; j++)
+				{
+					pixels[i * image->width + j] = image->pixels[i * image->width + j];
+				}
+			} 
+			std::vector<uint32_t> resizeBuffer( nDesiredWidth * nDesiredHeight );
+			stbir_resize_uint8_srgb( (unsigned char *)pixels.data(),       image->width,  image->height,  0,
+									 (unsigned char *)resizeBuffer.data(), nDesiredWidth, nDesiredHeight, 0,
+									 4, 3, STBIR_FLAG_ALPHA_PREMULTIPLIED );
+
+			cursorBuffer = std::make_shared<std::vector<uint32_t>>(surfaceWidth * surfaceHeight);
+			for (int i = 0; i < nDesiredHeight; i++) {
+				for (int j = 0; j < nDesiredWidth; j++) {
+					(*cursorBuffer)[i * surfaceWidth + j] = resizeBuffer[i * nDesiredWidth + j];
+
+					if ( (*cursorBuffer)[i * surfaceWidth + j] & 0xff000000 ) {
+						bNoCursor = false;
+					}
+				}
+			}
 
-				if ( (*cursorBuffer)[i * surfaceWidth + j] & 0xff000000 ) {
-					bNoCursor = false;
+			m_hotspotX = ( m_hotspotX * nDesiredWidth ) / image->width;
+			m_hotspotY = ( m_hotspotY * nDesiredHeight ) / image->height;
+
+			nContentWidth = nDesiredWidth;
+			nContentHeight = nDesiredHeight;
+		}
+		else
+		{
+			cursorBuffer = std::make_shared<std::vector<uint32_t>>(surfaceWidth * surfaceHeight);
+			for (int i = 0; i < image->height; i++) {
+				for (int j = 0; j < image->width; j++) {
+					(*cursorBuffer)[i * surfaceWidth + j] = image->pixels[i * image->width + j];
+
+					if ( (*cursorBuffer)[i * surfaceWidth + j] & 0xff000000 ) {
+						bNoCursor = false;
+					}
 				}
 			}
 		}
 	}
 
+
 	if (bNoCursor)
 		cursorBuffer = nullptr;
 
@@ -2049,14 +2077,27 @@ bool MouseCursor::getTexture()
 		// TODO: choose format & modifiers from cursor plane
 	}
 
-	m_texture = vulkan_create_texture_from_bits(surfaceWidth, surfaceHeight, image->width, image->height, DRM_FORMAT_ARGB8888, texCreateFlags, cursorBuffer->data());
-	sdlwindow_cursor(std::move(cursorBuffer), image->width, image->height, image->xhot, image->yhot);
+	m_texture = vulkan_create_texture_from_bits(surfaceWidth, surfaceHeight, nContentWidth, nContentHeight, DRM_FORMAT_ARGB8888, texCreateFlags, cursorBuffer->data());
+	sdlwindow_cursor(std::move(cursorBuffer), nDesiredWidth, nDesiredHeight, image->xhot, image->yhot);
 	assert(m_texture);
 	XFree(image);
 
 	return true;
 }
 
+void MouseCursor::GetDesiredSize( int& nWidth, int &nHeight )
+{
+	int nSize = g_nBaseCursorScale;
+	if ( g_nCursorScaleHeight > 0 )
+	{
+		nSize = nSize * floor(g_nOutputHeight / (float)g_nCursorScaleHeight);
+		nSize = std::clamp( nSize, g_nBaseCursorScale, 256 );
+	}
+
+	nWidth = nSize;
+	nHeight = nSize;
+}
+
 void MouseCursor::paint(steamcompmgr_win_t *window, steamcompmgr_win_t *fit, struct FrameInfo_t *frameInfo)
 {
 	if ( m_hideForMovement || m_imageEmpty ) {
@@ -2085,7 +2126,9 @@ void MouseCursor::paint(steamcompmgr_win_t *window, steamcompmgr_win_t *fit, str
 	float cursor_scale = 1.0f;
 	if ( g_nCursorScaleHeight > 0 )
 	{
-		cursor_scale = floor(currentOutputHeight / (float)g_nCursorScaleHeight);
+		int nDesiredWidth, nDesiredHeight;
+		GetDesiredSize( nDesiredWidth, nDesiredHeight );
+		cursor_scale = nDesiredHeight / (float)m_texture->contentHeight();
 	}
 	cursor_scale = std::max(cursor_scale, 1.0f);
 
@@ -7982,6 +8025,8 @@ steamcompmgr_main(int argc, char **argv)
 					XChangeProperty(server->ctx->dpy, server->ctx->root, server->ctx->atoms.gamescopeHDROutputFeedback, XA_CARDINAL, 32, PropModeReplace,
 						(unsigned char *)&hdr_value, 1 );
 
+					server->ctx->cursor->setDirty();
+
 					if (server->ctx.get() == root_ctx)
 					{
 						flush_root = true;

src/steamcompmgr.hpp

@@ -94,6 +94,8 @@ class MouseCursor
 	bool needs_server_flush() const { return m_needs_server_flush; }
 	void inform_flush() { m_needs_server_flush = false; }
 
+	void GetDesiredSize( int& nWidth, int &nHeight );
+
 private:
 	void warp(int x, int y);
 	void checkSuspension();