Add the ability to write Devices in Rust (#105)

* Start implementing custom devices

* Add clip functions to custom device

* Add more functions to custom device

* Rename to NativeDevice

* Add render_flags and layer

* Replace `mem::forget` with `ManuallyDrop`

* Add structure and metatext

* Start implementing tests

* Add safety comment and error handling

* Simplify function requirements

* Remove unused import

Author: ginnyTheCat

mupdf-sys/build.rs

@@ -118,8 +118,8 @@ fn build_libmupdf() {
     ];
 
     // this may be unused if none of the features below are enabled
-    #[allow(unused_variables)]
-    let add_lib = |cflags_name: &'static str, pkgcfg_name: &'static str| {
+    #[allow(unused_variables, unused_mut)]
+    let mut add_lib = |cflags_name: &'static str, pkgcfg_name: &'static str| {
         make_flags.push(format!(
             "SYS_{cflags_name}_CFLAGS={}",
             pkg_config::probe_library(pkgcfg_name)

mupdf-sys/src/lib.rs

@@ -4,3 +4,49 @@
 #![allow(clippy::all)]
 
 include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+
+use core::ffi::{c_int, CStr};
+
+/// This function allocates a new device and returns a pointer to it if no error occured. For the
+/// required structure of `T` check the example below. If an error occurs the pointer `errptr` points
+/// to will be set to to a pointer pointing to the error and null returned from this function.
+///
+/// # Safety
+///
+/// The caller must ensure `ctx` and `errptr` to be a valid pointers.
+///
+/// It must also ensure `T` to be a type that starts with `fz_device`. Memory will be allocated for
+/// a new instance of `T`, but only the `fz_device` portion will be initialized. The rest is
+/// currently being zero-initialized, but this might change in the future.
+///
+/// # Example
+///
+/// This is how a compliant `T` might look like. The `repr(C)` is necessary as `repr(Rust)` does
+/// not guarantee stable field orderings.
+///
+/// ```rust
+/// use mupdf_sys::fz_device;
+///
+/// #[repr(C)]
+/// struct MyDevice {
+///     base: fz_device,
+///     foo: u32,
+/// }
+/// ```
+pub unsafe fn mupdf_new_derived_device<T>(
+    ctx: *mut fz_context,
+    label: &'static CStr,
+    errptr: *mut *mut mupdf_error_t,
+) -> *mut T {
+    let SIZE: c_int = const {
+        if (c_int::MAX as usize) < size_of::<T>() {
+            panic!("device too big")
+        } else {
+            size_of::<T>() as c_int
+        }
+    };
+
+    let device = mupdf_new_device_of_size(ctx, SIZE, errptr);
+    let label = Memento_label(device.cast(), label.as_ptr());
+    label.cast()
+}

mupdf-sys/wrapper.c

@@ -2640,6 +2640,20 @@ fz_device *mupdf_new_draw_device(fz_context *ctx, fz_pixmap *pixmap, fz_irect cl
     return device;
 }
 
+fz_device *mupdf_new_device_of_size(fz_context *ctx, int size, mupdf_error_t **errptr)
+{
+    fz_device *device = NULL;
+    fz_try(ctx)
+    {
+        device = fz_new_device_of_size(ctx, size);
+    }
+    fz_catch(ctx)
+    {
+        mupdf_save_error(ctx, errptr);
+    }
+    return device;
+}
+
 fz_device *mupdf_new_display_list_device(fz_context *ctx, fz_display_list *list, mupdf_error_t **errptr)
 {
     fz_device *device = NULL;
@@ -2863,6 +2877,54 @@ void mupdf_end_layer(fz_context *ctx, fz_device *device, mupdf_error_t **errptr)
     }
 }
 
+void mupdf_begin_structure(fz_context *ctx, fz_device *device, fz_structure standard, const char *raw, int idx, mupdf_error_t **errptr)
+{
+    fz_try(ctx)
+    {
+        fz_begin_structure(ctx, device, standard, raw, idx);
+    }
+    fz_catch(ctx)
+    {
+        mupdf_save_error(ctx, errptr);
+    }
+}
+
+void mupdf_end_structure(fz_context *ctx, fz_device *device, mupdf_error_t **errptr)
+{
+    fz_try(ctx)
+    {
+        fz_end_structure(ctx, device);
+    }
+    fz_catch(ctx)
+    {
+        mupdf_save_error(ctx, errptr);
+    }
+}
+
+void mupdf_begin_metatext(fz_context *ctx, fz_device *device, fz_metatext meta, const char *text, mupdf_error_t **errptr)
+{
+    fz_try(ctx)
+    {
+        fz_begin_metatext(ctx, device, meta, text);
+    }
+    fz_catch(ctx)
+    {
+        mupdf_save_error(ctx, errptr);
+    }
+}
+
+void mupdf_end_metatext(fz_context *ctx, fz_device *device, mupdf_error_t **errptr)
+{
+    fz_try(ctx)
+    {
+        fz_end_metatext(ctx, device);
+    }
+    fz_catch(ctx)
+    {
+        mupdf_save_error(ctx, errptr);
+    }
+}
+
 void mupdf_begin_mask(fz_context *ctx, fz_device *device, fz_rect area, bool luminosity, fz_colorspace *cs, const float *color, fz_color_params cp, mupdf_error_t **errptr)
 {
     fz_try(ctx)
@@ -2875,11 +2937,11 @@ void mupdf_begin_mask(fz_context *ctx, fz_device *device, fz_rect area, bool lum
     }
 }
 
-void mupdf_end_mask(fz_context *ctx, fz_device *device, mupdf_error_t **errptr)
+void mupdf_end_mask(fz_context *ctx, fz_device *device, fz_function *fn, mupdf_error_t **errptr)
 {
     fz_try(ctx)
     {
-        fz_end_mask(ctx, device);
+        fz_end_mask_tr(ctx, device, fn);
     }
     fz_catch(ctx)
     {