Revert android to android 21

Author: alizahlalani

android/build.gradle

@@ -94,7 +94,7 @@ buildscript {
 
     ext.versions = [
         'jdk': 17,
-        'minSdk': 26,
+        'minSdk': 21,
         'targetSdk': 34,
         'compileSdk': 34,
         'kotlin': '2.0.21',
@@ -125,7 +125,7 @@ buildscript {
     ext.cmakeArgs = [
         "--no-warn-unused-cli",
         "-DANDROID_PIE=ON",
-        "-DANDROID_PLATFORM=26",
+        "-DANDROID_PLATFORM=21",
         "-DANDROID_STL=c++_static",
         "-DFILAMENT_DIST_DIR=${filamentPath}".toString(),
         "-DFILAMENT_SUPPORTS_VULKAN=${excludeVulkan ? 'OFF' : 'ON'}".toString(),

build/toolchain-aarch64-linux-android.cmake

@@ -21,7 +21,7 @@ set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_SYSTEM_VERSION 1)
 
 # android
-set(API_LEVEL 26)
+set(API_LEVEL 21)
 
 # architecture
 set(ARCH aarch64-linux-android)

build/toolchain-arm7-linux-android.cmake

@@ -21,7 +21,7 @@ set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_SYSTEM_VERSION 1)
 
 # android
-set(API_LEVEL 26)
+set(API_LEVEL 21)
 
 # architecture
 set(ARCH armv7a-linux-androideabi)

build/toolchain-x86-linux-android.cmake

@@ -21,7 +21,7 @@ set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_SYSTEM_VERSION 1)
 
 # android
-set(API_LEVEL 26)
+set(API_LEVEL 21)
 
 # architecture
 set(ARCH i686-linux-android)

build/toolchain-x86_64-linux-android.cmake

@@ -21,7 +21,7 @@ set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_SYSTEM_VERSION 1)
 
 # android
-set(API_LEVEL 26)
+set(API_LEVEL 21)
 
 # architecture
 set(ARCH x86_64-linux-android)

filament/backend/src/opengl/platforms/PlatformEGLAndroid.cpp

@@ -54,10 +54,11 @@
 #include <stdint.h>
 #include <stdlib.h>
 
-// We require filament to be built with an API 26 toolchain, before that,
-// AHardwareBuffer support didn't exist.
-#if __ANDROID_API__ < 26
-#error "__ANDROID_API__ must be at least 26"
+// We require filament to be built with an API 19 toolchain, before that, OpenGLES 3.0 didn't exist
+// Actually, OpenGL ES 3.0 was added to API 18, but API 19 is the better target and
+// the minimum for Jetpack at the time of this comment.
+#if __ANDROID_API__ < 21
+#error "__ANDROID_API__ must be at least 21"
 #endif
 
 using namespace utils;
@@ -235,18 +236,22 @@ PlatformEGLAndroid::ExternalImageEGLAndroid::~ExternalImageEGLAndroid() = defaul
 
 Platform::ExternalImageHandle PlatformEGLAndroid::createExternalImage(AHardwareBuffer const* buffer,
         bool sRGB) noexcept {
-    auto* const p = new (std::nothrow) ExternalImageEGLAndroid;
-    auto hardwareBuffer = const_cast<AHardwareBuffer*>(buffer);
-    p->aHardwareBuffer = hardwareBuffer;
-    p->sRGB = sRGB;
-    AHardwareBuffer_Desc hardwareBufferDescription = {};
-    AHardwareBuffer_describe(hardwareBuffer, &hardwareBufferDescription);
-    p->height = hardwareBufferDescription.height;
-    p->width = hardwareBufferDescription.width;
-    auto textureFormat = mapToFilamentFormat(hardwareBufferDescription.format, sRGB);
-    p->format = textureFormat;
-    p->usage = mapToFilamentUsage(hardwareBufferDescription.usage, textureFormat);
-    return ExternalImageHandle{ p };
+    if (__builtin_available(android 26, *)) {
+        auto* const p = new (std::nothrow) ExternalImageEGLAndroid;
+        auto hardwareBuffer = const_cast<AHardwareBuffer*>(buffer);
+        p->aHardwareBuffer = hardwareBuffer;
+        p->sRGB = sRGB;
+        AHardwareBuffer_Desc hardwareBufferDescription = {};
+        AHardwareBuffer_describe(hardwareBuffer, &hardwareBufferDescription);
+        p->height = hardwareBufferDescription.height;
+        p->width = hardwareBufferDescription.width;
+        auto textureFormat = mapToFilamentFormat(hardwareBufferDescription.format, sRGB);
+        p->format = textureFormat;
+        p->usage = mapToFilamentUsage(hardwareBufferDescription.usage, textureFormat);
+        return ExternalImageHandle{ p };
+    }
+
+    return Platform::ExternalImageHandle{};
 }
 
 bool PlatformEGLAndroid::setExternalImage(ExternalImageHandleRef externalImage,