| Summary: | DPI is always reported to 96 on High Res Display | ||
|---|---|---|---|
| Product: | [Applications] systemsettings | Reporter: | Kai-Uwe Behrmann <ku.b> |
| Component: | kcm_fonts | Assignee: | Unassigned bugs mailing-list <unassigned-bugs> |
| Status: | REPORTED --- | ||
| Severity: | normal | CC: | ivan, kde, ku.b, unassigned-bugs |
| Priority: | NOR | ||
| Version: | 5.5.2 | ||
| Target Milestone: | --- | ||
| Platform: | openSUSE | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed In: | ||
| Sentry Crash Report: | |||
The offending line is here: https://quickgit.kde.org/?p=plasma-desktop.git&a=blob&h=07297bb660e4fd16059978f3b0e539d377542de0&hb=6367245d25d521d498d1b0734f88d287e17e69b1&f=kcms%2Ffonts%2Ffonts.cpp line:710 #if HAVE_X11 checkboxForceDpi->setChecked(false); spinboxDpi->setValue(96); #endif Well, that's just the default value, if you don't set one, isn't it? Also, scaling through that KCM isn't recommended. Try the "Scale Display" option in Display settings instead. Where does this default of 96 DPI come from? Why not 72 DPI why not assume actual display resolution of 192 or 300dpi? "Scale Display" in the display section does not affect font renderings - unfortunately. It would be cool if it allows scaling with one setting. Instead now (5.4.3) users are forced to do three settings to adapt the desktop scaling: * set "Force fonts DPI:" and assign a proper DPI value * set "Scale Display" scale factor - not dpi: sig * set tool bar height outside of systemsettings again in a different unit - pixels Because 96dpi is the de-facto dpi standard for most "normal resolution" desktop monitors. The screen scaling settings also change Xft dpi, the same settings the force fonts dpi influences. Also, what do you mean by tool bar height? "Kontrollleiste" is it called in KDE/german. Dock in OS X. "Taskleiste" in Windows/german. (In reply to Kai Uwe Broulik from comment #4) > The screen scaling settings also change Xft dpi, the same settings the force > fonts dpi influences. Oh, that's then perhaps newer than the code I could test. Would be great. Ah panel. The panel was recently fixed to take dpi into account (In reply to Kai-Uwe Behrmann from comment #7) > (In reply to Kai Uwe Broulik from comment #4) > > The screen scaling settings also change Xft dpi, the same settings the force > > fonts dpi influences. > > Oh, that's then perhaps newer than the code I could test. Would be great. The screen scaling of kscreen does not handle any font, just window and icon sizes. I tested with kscreen 5.5.2 in KF-5.17. |
The plasma 5 systemsettings fontsettings panel has a checkbox for forcing a DPI value for fonts and a accompanying DPI value field. So far so good. On a MacBook-pro with retina display this field is always set to 96 DPI, which is wrong. This setting forces me to adjust the value manually to 192 doubling the size to obtain a reasonable desktop. The correct physical DPI value is 227. After some research for other non Qt based applications, I found that 96 is always reported by Xinerama on this machine, with all other values like size and so on computed to match 96 DPI. However XRandR reports the size in millimeter correctly. Based on this information and the desktops pixel size, the DPI can be computed correctly. Reproducible: Always Steps to Reproduce: 1. install KDE Plasma 5 on MacBookPro Retina 2. see the too small desktop windows rendering 3. go to systemsettings -> font settings -> force DPI box Actual Results: see 96 DPI in the fonts force DPI value box Expected Results: see the xrandr reported DPI value in the fonts force DPI value box // Here some code showing the correct DPI values by using the XRandR API. // Hope this helps. // cc -Wall -g -pedantic XRandRfl.cxx -o XRandRfl -lX11 `pkg-config --libs xrandr` #include <X11/extensions/Xrandr.h> #include <stdio.h> int main(int argc, char ** argv) { Display * display = XOpenDisplay(":0.0"); int screen = DefaultScreen( display ); Window w = RootWindow(display, screen); XRRScreenResources * res = XRRGetScreenResources(display, w); for(int i=0; i < res->noutput; ++i) { XRROutputInfo * output_info = XRRGetOutputInfo( display, res, res->outputs[i]); if(output_info->crtc) { XRRCrtcInfo * crtc_info = XRRGetCrtcInfo( display, res, output_info->crtc ); unsigned int pixel_width = crtc_info->width, pixel_height = crtc_info->height; float xdpi = pixel_width * 25.4f / (float)output_info->mm_width, ydpi = pixel_height * 25.4f / (float)output_info->mm_height; printf( "[%d] %upx x %upx Dimensions: %limm x %limm DPI: %.02f x %.02f\n", i, pixel_width, pixel_height, output_info->mm_width, output_info->mm_height, xdpi, ydpi ); } XRRFreeOutputInfo( output_info ); } XRRFreeScreenResources(res); XCloseDisplay( display ); return 0; }