From 8b478431a77a58b0200e5df33e4480a07b4e562a Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@slint.dev>
Date: Tue, 12 Sep 2023 11:05:58 +0200
Subject: [PATCH] Help the Skia build to find clang

..even if cmake sets CC/CXX to GCC.
---
 api/cpp/CMakeLists.txt | 82 +++++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 32 deletions(-)

diff --git a/api/cpp/CMakeLists.txt b/api/cpp/CMakeLists.txt
index 95cf11f94..e368cb848 100644
--- a/api/cpp/CMakeLists.txt
+++ b/api/cpp/CMakeLists.txt
@@ -204,39 +204,57 @@ else(SLINT_STYLE)
     set_property(GLOBAL PROPERTY SLINT_STYLE ${SLINT_STYLE_DEFAULT})
 endif(SLINT_STYLE)
 
-# The Skia cross-build requires a host C compiler (due to some build dependencies of rust-skia),
-# so cc.rs will first look for CC_<triplet> and then HOST_CC.
-# When cross-compiling, CMake doesn't really know what the host compiler is. Corrosion will set
-# HOST_CC to $CC, which is a good bet. Unfortunately in Yocto environments, CC will be set to
-# the cross-compiler. The same applies to CFLAGS, which may contain target specific options.
-# So the hack to solve this is two-fold:
-#  * We look for clang or gcc in PATH - unprefixed those are usually host compilers.
-#  * Through corrosion we know the correct host value of CC_<triplet>.
-# Finally, we set CC_<host triplet> to clang or gcc and empty CFLAGS_<host triplet>
-if((SLINT_FEATURE_RENDERER_SKIA OR SLINT_FEATURE_RENDERER_SKIA_OPENGL OR SLINT_FEATURE_RENDERER_SKIA_VULKAN) AND CMAKE_CROSSCOMPILING AND Rust_CARGO_HOST_TARGET)
-    find_program(CLANG clang)
-    if(CLANG)
-        set(host_cc "${CLANG}")
-    else()
-        find_program(GCC gcc)
-        if (GCC)
-            set(host_cc "${GCC}")
-        endif()
+if(SLINT_FEATURE_RENDERER_SKIA OR SLINT_FEATURE_RENDERER_SKIA_OPENGL OR SLINT_FEATURE_RENDERER_SKIA_VULKAN)
+    find_program(CLANGCC clang)
+    find_program(CLANGCXX clang++)
+    if(CLANGCC AND CLANGCXX)
+        set_property(
+            TARGET slint-cpp
+            APPEND
+            PROPERTY CORROSION_ENVIRONMENT_VARIABLES
+            CLANGCC=${CLANGCC}
+        )
+        set_property(
+            TARGET slint-cpp
+            APPEND
+            PROPERTY CORROSION_ENVIRONMENT_VARIABLES
+            CLANGCXX=${CLANGCXX}
+        )    
     endif()
-    if(host_cc)
-        string(REPLACE "-" "_" cargo_host_target_underscore "${Rust_CARGO_HOST_TARGET}")
-        set_property(
-            TARGET slint-cpp
-            APPEND
-            PROPERTY CORROSION_ENVIRONMENT_VARIABLES
-            CC_${cargo_host_target_underscore}=${host_cc}
-        )
-        set_property(
-            TARGET slint-cpp
-            APPEND
-            PROPERTY CORROSION_ENVIRONMENT_VARIABLES
-            CFLAGS_${cargo_host_target_underscore}=
-        )
+
+    # The Skia cross-build requires a host C compiler (due to some build dependencies of rust-skia),
+    # so cc.rs will first look for CC_<triplet> and then HOST_CC.
+    # When cross-compiling, CMake doesn't really know what the host compiler is. Corrosion will set
+    # HOST_CC to $CC, which is a good bet. Unfortunately in Yocto environments, CC will be set to
+    # the cross-compiler. The same applies to CFLAGS, which may contain target specific options.
+    # So the hack to solve this is two-fold:
+    #  * We look for clang or gcc in PATH - unprefixed those are usually host compilers.
+    #  * Through corrosion we know the correct host value of CC_<triplet>.
+    # Finally, we set CC_<host triplet> to clang or gcc and empty CFLAGS_<host triplet>
+    if(CMAKE_CROSSCOMPILING AND Rust_CARGO_HOST_TARGET)
+        if(CLANGCC)
+            set(host_cc "${CLANGCC}")
+        else()
+            find_program(GCC gcc)
+            if (GCC)
+                set(host_cc "${GCC}")
+            endif()
+        endif()
+        if(host_cc)
+            string(REPLACE "-" "_" cargo_host_target_underscore "${Rust_CARGO_HOST_TARGET}")
+            set_property(
+                TARGET slint-cpp
+                APPEND
+                PROPERTY CORROSION_ENVIRONMENT_VARIABLES
+                CC_${cargo_host_target_underscore}=${host_cc}
+            )
+            set_property(
+                TARGET slint-cpp
+                APPEND
+                PROPERTY CORROSION_ENVIRONMENT_VARIABLES
+                CFLAGS_${cargo_host_target_underscore}=
+            )
+        endif()
     endif()
 endif()