fix c api, add usage example

examples/lang_c/CMakeLists.txt

@@ -0,0 +1,23 @@
+cmake_minimum_required(VERSION 3.28)
+project(lang_c C)
+set(CMAKE_C_STANDARD 17)
+
+include(FetchContent)
+FetchContent_Declare(
+        Corrosion
+        GIT_REPOSITORY https://github.com/corrosion-rs/corrosion.git
+        GIT_TAG v0.5 # Optionally specify a commit hash, version tag or branch here
+)
+FetchContent_MakeAvailable(Corrosion)
+
+# Import targets defined in a package or workspace manifest `Cargo.toml` file
+corrosion_import_crate(
+        MANIFEST_PATH ../../servicepoint2/Cargo.toml
+        PROFILE release
+        FEATURES c-api
+        ALL_FEATURES)
+
+add_executable(lang_c main.c)
+
+target_link_libraries(lang_c PRIVATE servicepoint2)
+

examples/lang_c/main.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include "../../servicepoint2/sp2-bindings.h"
+
+int main(void) {
+    sp2_Connection *connection = sp2_connection_open("localhost:2342");
+    if (connection == NULL)
+        return 1;
+
+    sp2_Command *command = sp2_command_clear();
+    if (command == NULL)
+        return 2;
+    if (!sp2_connection_send(connection, command))
+        return 3;
+
+    sp2_PixelGrid *pixels = sp2_pixel_grid_new(sp2_PIXEL_WIDTH, sp2_PIXEL_HEIGHT);
+    sp2_pixel_grid_fill(pixels, true);
+    command = sp2_command_bitmap_linear_win(0, 0, pixels);
+    if (command == NULL)
+        return 4;
+    if (!sp2_connection_send(connection, command))
+        return 5;
+
+    sp2_connection_dealloc(connection);
+    return 0;
+}