DpiScale

DpiScale

This sample showcases a UI that is DPI aware vs one rendered using the standard pixel based method.

It also showcases various ways to render scaled strings and the errors that are easy to introduce.

Controls

The app can be controlled using:

Key	Result
P	Toggle pixel perfect rendering on/off
T	Toggle test pattern on/off
U	Toggle UI test pattern on/off
D	Toggle emulate dpi on/off
Delete	dpi slider decrease by one
Page down	dpi slider increase by one
Left arrow	dpi slider decrease
Right arrow	dpi slider increase
F	Force texture DPI on/off
Up arrow	Increase texture dpi
Down arrow	Decrease texture dpi
Q	Slider downscale preference decrease
E	Slider downscale preference increase
Space	Reset settings to default

Example 1 - Blurry

Texture rendered at native resolution but off by 0.5 pixel

Texture 160dpi Scale 1.00

Native	4x zoom

Example 2 - Details

Texture downscaled but small details gets lost and glyphs gets slightly blurred

Texture 320dpi Scale 0.75

Native	4x zoom

Example 3 - String scaling issues

Reference texture 160dpi scale 1.0

Native	4x zoom

Texture 160dpi scale 0.8375

#	Native	4x zoom
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6
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8

1. Naive scaling of everything. This is basically a font position * scale factor.
   • Not pixel perfect so the text is blurry due to characters being rendered to sub pixel positions.
   • Very small glyphs can be reduced to a size of zero.
2. We ensure that each glyph is starts and ends at a full pixel
   • glyph width and height might be slightly off.
   • Glyphs do not hit the correct position on the baseline.
   • Line width compared to the naively scaled one is off.
   • Very small glyphs can be reduced to a size of zero.
3. Baseline aware and we ensure that each glyph is starts and ends at a full pixel
   • glyph width and height might be slightly off.
   • Line width compared to the naively scaled one is off.
   • Simple kerning is inaccurate.
   • Very small glyphs can be reduced to a size of zero.
4. Baseline aware and we ensure that each glyph is starts and ends at a full pixel. FontWidth & layoutWidth is scaled and rounded to a full pixel (so the font is pixel perfect in width).
   • On some scalings the glyph alignment to the baseline is off by one pixel.
   • Glyph width and height might be slightly off.
   • The simple kerning is slightly off.
   • Very small glyphs can be reduced to a size of zero.
5. Baseline aware and we ensure that each glyph is starts and ends at a full pixel. FontWidth & layoutWidth is scaled and rounded to a full pixel and more precise height scaling (pixel perfect width and height).
   • Glyph width and height might be slightly off.
   • The simple kerning is slightly off.
   • Very small glyphs can be reduced to a size of zero.
6. Baseline aware and we ensure that each glyph is starts and ends at a full pixel. FontWidth & layoutWidth is scaled and rounded to a full pixel and more precise height scaling (pixel perfect width and height). We ensure a glyph cant be smaller than one pixel.
   • Glyph width and height might be slightly off.
   • The simple kerning is slightly off.
7. Same as 6 except rendered using the demo framework string rendering. The output should be exactly the same as 6, and it has the same issues as well.

Another example

Reference texture 480dpi scale 1.0

Native	4x zoom

Texture 480dpi scale 0.8333333

#	Native	4x zoom
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Command line arguments':

Argument	Description	Source
--TestPattern	Enable the test pattern	Demo
--UITestPattern	Enable the UI test pattern	Demo
--ActualDpi <arg>	ActualDpi [x,y] Override the actual dpi reported by the native window	DemoHost
--DensityDpi <arg>	DensityDpi <number> Override the density dpi reported by the native window	DemoHost
--DisplayId <arg>	DisplayId <number>	DemoHost
--LogExtensions	Output the extensions to the log	DemoHost
--LogLayers	Output the layers to the log	DemoHost
--LogSurfaceFormats	Output the supported surface formats to the log	DemoHost
--VkApiDump	Enable the VK_LAYER_LUNARG_api_dump layer.	DemoHost
--VkPhysicalDevice <arg>	Set the physical device index.	DemoHost
--VkPresentMode <arg>	Override the present mode with the supplied value. Known values: VK_PRESENT_MODE_IMMEDIATE_KHR (0), VK_PRESENT_MODE_MAILBOX_KHR (1), VK_PRESENT_MODE_FIFO_KHR (2), VK_PRESENT_MODE_FIFO_RELAXED_KHR (3), VK_PRESENT_MODE_SHARED_DEMAND_REFRESH_KHR (1000111000), VK_PRESENT_MODE_SHARED_CONTINUOUS_REFRESH_KHR (1000111001)	DemoHost
--VkScreenshot <arg>	Enable/disable screenshot support (defaults to enabled)	DemoHost
--VkValidate <arg>	Enable/disable the VK_LAYER_LUNARG_standard_validation layer.	DemoHost
--Window <arg>	Window mode [left,top,width,height]	DemoHost
--AppFirewall	Enable the app firewall, reporting crashes on-screen instead of exiting	DemoHostManager
--ContentMonitor	Monitor the Content directory for changes and restart the app on changes.WARNING: Might not work on all platforms and it might impact app performance (experimental)	DemoHostManager
--ExitAfterDuration <arg>	Exit after the given duration has passed. The value can be specified in seconds or milliseconds. For example 10s or 10ms.	DemoHostManager
--ExitAfterFrame <arg>	Exit after the given number of frames has been rendered	DemoHostManager
--ForceUpdateTime <arg>	Force the update time to be the given value in microseconds (can be useful when taking a lot of screen-shots). If 0 this option is disabled	DemoHostManager
--LogStats	Log basic rendering stats (this is equal to setting LogStatsMode to latest)	DemoHostManager
--LogStatsMode <arg>	Set the log stats mode, more advanced version of LogStats. Can be disabled, latest, average	DemoHostManager
--ScreenshotFormat <arg>	Chose the format for the screenshot: bmp, jpg, png (default), tga	DemoHostManager
--ScreenshotFrequency <arg>	Create a screenshot at the given frame frequency	DemoHostManager
--ScreenshotNamePrefix <arg>	Chose the screenshot name prefix (defaults to 'Screenshot')	DemoHostManager
--ScreenshotNameScheme <arg>	Chose the screenshot name scheme: frame (default), sequence, exact.	DemoHostManager
--Stats	Display basic frame profiling stats	DemoHostManager
--StatsFlags <arg>	Select the stats to be displayed/logged. Defaults to frame|cpu. Can be 'frame', 'cpu' or any combination	DemoHostManager
--Version	Print version information	DemoHostManager
--Graphics.Profile	Enable graphics service stats	GraphicsService
--Profiler.AverageEntries <arg>	The number of frames used to calculate the average frame-time. Defaults to: 60	ProfilerService
--ghelp <arg>	Display option groups: all, demo or host	base
-h, --help	Display options	base
-v, --verbose	Enable verbose output	base