v: support better separation of general Android vs Termux specific code (part 2)

vlib/gg/gg_android_outside_termux.c.v

@@ -0,0 +1,38 @@
+module gg
+
+import sokol.sapp
+
+#include <android/configuration.h>
+#include <android/native_activity.h>
+
+fn C.AConfiguration_new() voidptr
+fn C.AConfiguration_fromAssetManager(voidptr, voidptr)
+fn C.AConfiguration_getDensity(voidptr) u32
+fn C.AConfiguration_delete(voidptr)
+
+struct C.AAssetManager {}
+
+// See https://developer.android.com/ndk/reference/struct/a-native-activity for more info.
+struct C.ANativeActivity {
+pub:
+	assetManager     voidptr // Pointer to the Asset Manager instance for the application. (AAssetManager *)
+	callbacks        voidptr // Pointer to the callback function table of the native application. (struct ANativeActivityCallbacks *)
+	clazz            voidptr // The NativeActivity object handle.
+	env              voidptr // JNI context for the main thread of the app.
+	externalDataPath &char   // Path to this application's external (removable/mountable) data directory.
+	instance         voidptr // This is the native instance of the application.
+	internalDataPath &char   // Path to this application's internal data directory.
+	obbPath          &char   // Available starting with Honeycomb: path to the directory containing the application's OBB files (if any).
+	sdkVersion       int     // The platform's SDK version code.
+	vm               voidptr // The global handle on the process's Java VM
+}
+
+// android_dpi_scale returns the scale factor of the device.
+pub fn android_dpi_scale() f32 {
+	config := C.AConfiguration_new()
+	activity := &C.ANativeActivity(sapp.android_get_native_activity())
+	C.AConfiguration_fromAssetManager(config, activity.assetManager)
+	density := C.AConfiguration_getDensity(config)
+	C.AConfiguration_delete(config)
+	return f32(density) / 160
+}