Add validate-backend-options.cmake script (#3828)

Co-authored-by: Frank Elsinga <frank@elsinga.de>

CMakeLists.txt

@@ -21,14 +21,7 @@ option(MLN_TEXT_SHAPING_HARFBUZZ "Use haffbuzz to shape complex text" ON)
 option(MLN_CORE_INCLUDE_DEPS "Include depdendencies in static build of core" OFF)
 option(MLN_CREATE_AUTORELEASEPOOL "Create autoreleasepool in render loop" OFF)
 
-if (MLN_LEGACY_RENDERER)
+include(cmake/validate-backend-options.cmake)
-    message(FATAL "The legacy renderer is no longer supported")
-endif()
-
-if (MLN_DRAWABLE_RENDERER)
-    message(FATAL "Do not pass MLN_DRAWABLE_RENDERER, the drawable renderer is now the default")
-endif()
-
 include(cmake/clang-tidy.cmake)
 
 if (MLN_WITH_QT AND NOT CMAKE_OSX_DEPLOYMENT_TARGET)

cmake/validate-backend-options.cmake

@@ -0,0 +1,28 @@
+if (MLN_LEGACY_RENDERER)
+  message(FATAL "The legacy renderer is no longer supported")
+endif()
+
+if (MLN_DRAWABLE_RENDERER)
+  message(FATAL "Do not pass MLN_DRAWABLE_RENDERER, the drawable renderer is now the default")
+endif()
+
+set(backend_count 0)
+if (MLN_WITH_OPENGL)
+  math(EXPR backend_count "${backend_count} + 1")
+endif()
+if (MLN_WITH_METAL)
+  math(EXPR backend_count "${backend_count} + 1")
+endif()
+if (MLN_WITH_VULKAN)
+  math(EXPR backend_count "${backend_count} + 1")
+endif()
+
+if (backend_count EQUAL 0)
+  message(FATAL_ERROR
+    "You need to set a rendering backend. "
+    "Set exactly one of: MLN_WITH_OPENGL, MLN_WITH_METAL, or MLN_WITH_VULKAN.")
+elseif (backend_count GREATER 1)
+  message(FATAL_ERROR
+    "Multiple rendering backends selected. "
+    "Please enable only one of: MLN_WITH_OPENGL, MLN_WITH_METAL, or MLN_WITH_VULKAN.")
+endif()

platform/android/MapLibreAndroidTestApp/build.gradle.kts

@@ -79,9 +79,19 @@ android {
     productFlavors {
         create("opengl") {
             dimension = "renderer"
+            externalNativeBuild {
+                cmake {
+                    arguments("-DMLN_WITH_OPENGL=ON", "-DMLN_WITH_VULKAN=OFF")
+                }
+            }
         }
         create("vulkan") {
             dimension = "renderer"
+            externalNativeBuild {
+                cmake {
+                    arguments("-DMLN_WITH_OPENGL=OFF", "-DMLN_WITH_VULKAN=ON")
+                }
+            }
         }
     }