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Fixed bug 4883 - Add approximation for display DPI on iOS
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Aaron Barany

There appears to be no way to directly access the display DPI on iOS, so as an approximation the DPI for the iPhone 1 is used as a base value and is multiplied by the screen's scale. This should at least give a ballpark number for the various screen scales. (based on https://stackoverflow.com/questions/25756087/detecting-iphone-6-6-screen-sizes-in-point-values it appears that both 2x and 3x are used)

I have updated the patch to use a table of current devices and use a computation as a fallback. I have also updated the fallback computation to be more accurate.
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@slouken
slouken committed Dec 8, 2019
1 parent 54748a3 commit 140918b
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Showing 2 changed files with 167 additions and 3 deletions.
4 changes: 4 additions & 0 deletions src/video/uikit/SDL_uikitmodes.h
View file
Expand Up @@ -27,7 +27,10 @@

@interface SDL_DisplayData : NSObject

- (instancetype)init;

@property (nonatomic, strong) UIScreen *uiscreen;
@property (nonatomic) float screenDPI;

@end

Expand All @@ -41,6 +44,7 @@ extern SDL_bool UIKit_IsDisplayLandscape(UIScreen *uiscreen);

extern int UIKit_InitModes(_THIS);
extern void UIKit_GetDisplayModes(_THIS, SDL_VideoDisplay * display);
extern int UIKit_GetDisplayDPI(_THIS, SDL_VideoDisplay * display, float * ddpi, float * hdpi, float * vdpi);
extern int UIKit_SetDisplayMode(_THIS, SDL_VideoDisplay * display, SDL_DisplayMode * mode);
extern void UIKit_QuitModes(_THIS);
extern int UIKit_GetDisplayUsableBounds(_THIS, SDL_VideoDisplay * display, SDL_Rect * rect);
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166 changes: 163 additions & 3 deletions src/video/uikit/SDL_uikitmodes.m
View file
Expand Up @@ -27,9 +27,150 @@

#include "../../events/SDL_events_c.h"

#import <sys/utsname.h>

@implementation SDL_DisplayData

- (instancetype)initWithScreen:(UIScreen*)screen
{
if (self = [super init]) {
self.uiscreen = screen;

/*
* A well up to date list of device info can be found here:
* https://github.com/lmirosevic/GBDeviceInfo/blob/master/GBDeviceInfo/GBDeviceInfo_iOS.m
*/
NSDictionary* devices = @{
@"iPhone1,1": @163,
@"iPhone1,2": @163,
@"iPhone2,1": @163,
@"iPhone3,1": @326,
@"iPhone3,2": @326,
@"iPhone3,3": @326,
@"iPhone4,1": @326,
@"iPhone5,1": @326,
@"iPhone5,2": @326,
@"iPhone5,3": @326,
@"iPhone5,4": @326,
@"iPhone6,1": @326,
@"iPhone6,2": @326,
@"iPhone7,1": @401,
@"iPhone7,2": @326,
@"iPhone8,1": @326,
@"iPhone8,2": @401,
@"iPhone8,4": @326,
@"iPhone9,1": @326,
@"iPhone9,2": @401,
@"iPhone9,3": @326,
@"iPhone9,4": @401,
@"iPhone10,1": @326,
@"iPhone10,2": @401,
@"iPhone10,3": @458,
@"iPhone10,4": @326,
@"iPhone10,5": @401,
@"iPhone10,6": @458,
@"iPhone11,2": @458,
@"iPhone11,4": @458,
@"iPhone11,6": @458,
@"iPhone11,8": @326,
@"iPhone12,1": @326,
@"iPhone12,3": @458,
@"iPhone12,5": @458,
@"iPad1,1": @132,
@"iPad2,1": @132,
@"iPad2,2": @132,
@"iPad2,3": @132,
@"iPad2,4": @132,
@"iPad2,5": @163,
@"iPad2,6": @163,
@"iPad2,7": @163,
@"iPad3,1": @264,
@"iPad3,2": @264,
@"iPad3,3": @264,
@"iPad3,4": @264,
@"iPad3,5": @264,
@"iPad3,6": @264,
@"iPad4,1": @264,
@"iPad4,2": @264,
@"iPad4,3": @264,
@"iPad4,4": @326,
@"iPad4,5": @326,
@"iPad4,6": @326,
@"iPad4,7": @326,
@"iPad4,8": @326,
@"iPad4,9": @326,
@"iPad5,1": @326,
@"iPad5,2": @326,
@"iPad5,3": @264,
@"iPad5,4": @264,
@"iPad6,3": @264,
@"iPad6,4": @264,
@"iPad6,7": @264,
@"iPad6,8": @264,
@"iPad6,11": @264,
@"iPad6,12": @264,
@"iPad7,1": @264,
@"iPad7,2": @264,
@"iPad7,3": @264,
@"iPad7,4": @264,
@"iPad7,5": @264,
@"iPad7,6": @264,
@"iPad7,11": @264,
@"iPad7,12": @264,
@"iPad8,1": @264,
@"iPad8,2": @264,
@"iPad8,3": @264,
@"iPad8,4": @264,
@"iPad8,5": @264,
@"iPad8,6": @264,
@"iPad8,7": @264,
@"iPad8,8": @264,
@"iPad11,1": @326,
@"iPad11,2": @326,
@"iPad11,3": @326,
@"iPad11,4": @326,
@"iPod1,1": @163,
@"iPod2,1": @163,
@"iPod3,1": @163,
@"iPod4,1": @326,
@"iPod5,1": @326,
@"iPod7,1": @326,
@"iPod9,1": @326,
};

struct utsname systemInfo;
uname(&systemInfo);
NSString* deviceName =
[NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding];
id foundDPI = devices[deviceName];
if (foundDPI) {
self.screenDPI = (float)[foundDPI integerValue];
} else {
/*
* Estimate the DPI based on the screen scale multiplied by the base DPI for the device
* type (e.g. based on iPhone 1 and iPad 1)
*/
#if __IPHONE_OS_VERSION_MIN_REQUIRED >= 80000
float scale = (float)screen.nativeScale;
#else
float scale = (float)screen.scale;
#endif
float defaultDPI;
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
defaultDPI = 132.0f;
} else if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
defaultDPI = 163.0f;
} else {
defaultDPI = 160.0f;
}
self.screenDPI = scale * defaultDPI;
}
}
return self;
}

@synthesize uiscreen;
@synthesize screenDPI;

@end

Expand Down Expand Up @@ -153,14 +294,12 @@ @implementation SDL_DisplayModeData
display.current_mode = mode;

/* Allocate the display data */
SDL_DisplayData *data = [[SDL_DisplayData alloc] init];
SDL_DisplayData *data = [[SDL_DisplayData alloc] initWithScreen:uiscreen];
if (!data) {
UIKit_FreeDisplayModeData(&display.desktop_mode);
return SDL_OutOfMemory();
}

data.uiscreen = uiscreen;

display.driverdata = (void *) CFBridgingRetain(data);
SDL_AddVideoDisplay(&display);

Expand Down Expand Up @@ -243,6 +382,27 @@ @implementation SDL_DisplayModeData
}
}

int
UIKit_GetDisplayDPI(_THIS, SDL_VideoDisplay * display, float * ddpi, float * hdpi, float * vdpi)
{
@autoreleasepool {
SDL_DisplayData *data = (__bridge SDL_DisplayData *) display->driverdata;
float dpi = data.screenDPI;

if (ddpi) {
*ddpi = dpi * (float)SDL_sqrt(2.0);
}
if (hdpi) {
*hdpi = dpi;
}
if (vdpi) {
*vdpi = dpi;
}
}

return 0;
}

int
UIKit_SetDisplayMode(_THIS, SDL_VideoDisplay * display, SDL_DisplayMode * mode)
{
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