- cmake: remove zintconfig.h.in for now as incompatible with MSVC

project builds (will add back in future if go fully CMake)
- NO_PNG -> ZINT_NO_PNG and new API function `Zint_NoPng()` to
  determine if no PNG support in libzint; replace use in GUI with
  backend_qt method `noPng()`

backend/tests/CMakeLists.txt

@@ -25,12 +25,18 @@ if(ZINT_SHARED)
     add_library(testcommon ${testcommon_SRCS})
     target_link_libraries(testcommon zint)
     target_include_directories(testcommon PUBLIC ${zint_backend_tests_SOURCE_DIR})
+    if(NOT (ZINT_USE_PNG AND PNG_FOUND))
+        target_compile_definitions(testcommon PRIVATE ZINT_NO_PNG)
+    endif()
 endif()
 
 if(ZINT_STATIC)
     add_library(testcommon-static ${testcommon_SRCS})
     target_link_libraries(testcommon-static zint-static)
     target_include_directories(testcommon-static PUBLIC ${zint_backend_tests_SOURCE_DIR})
+    if(NOT (ZINT_USE_PNG AND PNG_FOUND))
+        target_compile_definitions(testcommon-static PRIVATE ZINT_NO_PNG)
+    endif()
 endif()
 
 zint_add_test(2of5 test_2of5)

backend/tests/test_print.c

@@ -102,9 +102,9 @@ static void test_print(const testCtx *const p_ctx) {
     }
 
     for (j = 0; j < exts_size; j++) {
-#ifdef NO_PNG
-        if (strcmp(exts[j], "png") == 0) continue;
-#endif
+
+        if (ZBarcode_NoPng() && strcmp(exts[j], "png") == 0) continue;
+
         assert_nonzero(sizeof(data_subdir) > strlen(data_dir) + 1 + strlen(exts[j]),
             "sizeof(data_subdir) (%d) <= strlen(data_dir) (%d) + 1 + strlen(%s) (%d)\n",
             (int) sizeof(data_subdir), (int) strlen(data_dir), exts[j], (int) strlen(exts[j]));

backend/tests/testcommon.c

@@ -38,7 +38,7 @@
 #include <windows.h>
 #include <direct.h>
 #endif
-#ifndef NO_PNG
+#ifndef ZINT_NO_PNG
 #include <png.h>
 #include <zlib.h>
 #include <setjmp.h>
@@ -1363,7 +1363,7 @@ int testUtilRename(const char *oldpath, const char *newpath) {
 /* Compare 2 PNG files */
 int testUtilCmpPngs(const char *png1, const char *png2) {
     int ret = -1;
-#ifdef NO_PNG
+#ifdef ZINT_NO_PNG
     (void)png1; (void)png2;
 #else
     FILE *fp1;