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Fixed bug 4883 - Add approximation for display DPI on iOS

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 committed Dec 8, 2019
1 parent 54748a3 commit 140918bb6fbb7d710da204012f9e4657329444a3
Showing with 167 additions and 3 deletions.
  1. +4 −0 src/video/uikit/SDL_uikitmodes.h
  2. +163 −3 src/video/uikit/SDL_uikitmodes.m
@@ -27,7 +27,10 @@

@interface SDL_DisplayData : NSObject

- (instancetype)init;

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

@end

@@ -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);
@@ -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

@@ -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);

@@ -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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