HiDPI improvements in Windows 10
Unlike previous versions of Windows (including Windows 7 which is still used on almost 50% of computers), Windows 10 contains a bunch of quality improvements related to scaling user interface of outdated applications incompatible with HiDPI (High-DPI) screen modes often used together with 4K monitors:
- scaling old applications with no blur at integer zooms;
- overriding DPI mode of an application in an arbitrary direction;
- quality scaling of text rendered via GDI;
- developers: ability to combine different DPI modes in the same application.
UI of HiDPI-incompatible applications at integer OS-level zooms is now scaled by simple pixel duplication — with no unreasonable blur. For example, at zoom of 200%, one logical pixel of application’s interface is rendered as a group of 4 (2×2) identical pixels corresponding to OS resolution, and at zoom of 300% — 9 pixels (3×3).
Blur that did before take place regardless of zoom ratios, now appears only at fractional zooms — e. g. 150% (1.5x) and 250% (2.5x), when interpolation and subsequent sharpness loss are really inevitable.
Overriding application’s DPI awareness
Beginning with one of preliminary builds (probably 15002) of Windows 10 Insider Preview, it’s now possible to override HiDPI compability (DPI awareness) of an application in an arbitrary direction.
Before, it was possible to disable DPI scaling (scaling by OS) only for applications formally not supporting HiDPI while actually working quite correctly in HiDPI mode.
Now it’s possible, when needed, to forcedly enable DPI scaling for applications that declare HiDPI support while actually not taking any actions for scaling the application’s interface, de facto oriented to system-resolution pixels and therefore rendered at very small size by default (for example, at zoom of 200% — 4 times smaller than needed) or incorrectly. Examples of such applications are Samsung Magician, control panel of the ESI Juli@ sound card, and Acronis True Image Home 2011.
Quality scaling of text
Beginning with the build 15002 of Windows 10 Insider Preview released in early 2017, the new “System (Enhanced)” mode is available for OS-powered scaling. In this mode, text in elements rendered via GDI is output at full system resolution, with no blur or pixelation.
The “System (Enhanced)” option is available via the dropdown list of the “Override high DPI scaling behavior. Scaling performed by” option in the “Compatibility” tab in properties of the executable.
For example, HWMonitor application in this mode looks and works almost the same as if it actually supported HiDPI, and, unlike forced HiDPI mode, there is no issue related to setting too small width of columns in the data table that comprises the main part of the application’s user interface.
Different DPI modes for windows of the same application
Beginning with Windows 10 Anniversary Update released in summer 2016, developers can now control DPI mode per window in the same application (Mixed Mode DPI Scaling).
This allows to implement HiDPI support in existing complex applications gradually, with no need for adapting the entire application at once.
Nonblurry full-screen scaling?
The only missing feature that owners of 4K monitors need to be absolutely happy is now probably full-screen nonblurry scaling by graphics drivers to prevent image-quality loss in such applications as games running at resolutions that are integer times lower than physical monitor resolution (for example, 1920×1080 or 1280×720 at physical resolution of 3840×2160).