[RFC] Filetype detection without extension (#77)

* first draft of filetype detection

* Nix: add file dependency

* Fix coding style mistake

* Manually format my code

---------

Co-authored-by: Mihai Fufezan <fufexan@protonmail.com>

CMakeLists.txt

@@ -64,6 +64,7 @@ target_link_libraries(hyprpaper
         OpenGL
         GLESv2
         pthread
+        magic
         ${CMAKE_THREAD_LIBS_INIT}
         ${CMAKE_SOURCE_DIR}/wlr-layer-shell-unstable-v1-protocol.o
         ${CMAKE_SOURCE_DIR}/xdg-shell-protocol.o

nix/default.nix

@@ -5,6 +5,7 @@
   cmake,
   ninja,
   cairo,
+  file,
   fribidi,
   libdatrie,
   libjpeg,
@@ -34,6 +35,7 @@ stdenv.mkDerivation {
 
   buildInputs = [
     cairo
+    file
     fribidi
     libdatrie
     libjpeg

src/render/WallpaperTarget.cpp

@@ -1,5 +1,7 @@
 #include "WallpaperTarget.hpp"
 
+#include <magic.h>
+
 CWallpaperTarget::~CWallpaperTarget() {
     cairo_surface_destroy(m_pCairoSurface);
 }
@@ -17,8 +19,22 @@ void CWallpaperTarget::create(const std::string& path) {
         CAIROSURFACE = JPEG::createSurfaceFromJPEG(path);
         m_bHasAlpha = false;
     } else {
-        Debug::log(CRIT, "unrecognized image %s", path.c_str());
-        exit(1);
+        // magic is slow, so only use it when no recognized extension is found
+        auto handle = magic_open(MAGIC_NONE|MAGIC_COMPRESS);
+        magic_load(handle, nullptr);
+
+        const auto type_str = std::string(magic_file(handle, path.c_str()));
+        const auto first_word = type_str.substr(0, type_str.find(" "));
+
+        if (first_word == "PNG") {
+            CAIROSURFACE = cairo_image_surface_create_from_png(path.c_str());
+        } else if (first_word == "JPEG") {
+            CAIROSURFACE = JPEG::createSurfaceFromJPEG(path);
+            m_bHasAlpha = false;
+        } else {
+            Debug::log(CRIT, "unrecognized image %s", path.c_str());
+            exit(1);
+        }
     }
 
     if (cairo_surface_status(CAIROSURFACE) != CAIRO_STATUS_SUCCESS) {