examples: C interop for HTML to PDF conversion using libwkhtmltox (#7751)

.github/workflows/ci.yml

@@ -80,6 +80,10 @@ jobs:
            sudo apt-get install --quiet -y libssl-dev sqlite3 libsqlite3-dev valgrind
            sudo apt-get install --quiet -y libglfw3 libglfw3-dev  libfreetype6-dev  libxi-dev libxcursor-dev libasound2-dev
            ## sudo apt-get install --quiet -y libsdl2-dev libsdl2-ttf-dev libsdl2-mixer-dev libsdl2-image-dev
+           ## The following is needed for examples/wkhtmltopdf.v
+           wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox_0.12.6-1.focal_amd64.deb
+           sudo apt-get install xfonts-75dpi xfonts-base
+           sudo dpkg -i wkhtmltox_0.12.6-1.focal_amd64.deb
     - name: Build v
       run: |
         echo $VFLAGS

cmd/tools/modules/testing/common.v

@@ -8,6 +8,8 @@ import sync
 import v.pref
 import v.util.vtest
 
+const github_job = os.getenv('GITHUB_JOB')
+
 pub struct TestSession {
 pub mut:
 	files         []string
@@ -113,6 +115,9 @@ pub fn new_test_session(_vargs string) TestSession {
 	$if windows {
 		skip_files << 'examples/x/websocket/ping.v' // requires OpenSSL
 	}
+	if github_job != 'ubuntu-tcc' {
+		skip_files << 'examples/wkhtmltopdf.v' // needs installation of wkhtmltopdf from https://github.com/wkhtmltopdf/packaging/releases
+	}
 	vargs := _vargs.replace('-progress', '').replace('-progress', '')
 	vexe := pref.vexe_path()
 	new_vtmp_dir := setup_new_vtmp_folder()

examples/wkhtmltopdf.v

@@ -0,0 +1,94 @@
+import os
+
+// Example of C interop for a very handy task.
+// 
+// wkhtmltopdf and wkhtmltoimage are open source (LGPLv3) command line tools to
+// render HTML into PDF and various image formats using the Qt WebKit rendering
+// engine. These run entirely "headless" and do not require a display or display
+// service.
+// 
+// https://github.com/wkhtmltopdf/wkhtmltopdf
+// https://wkhtmltopdf.org/downloads.html
+// https://wkhtmltopdf.org/libwkhtmltox/
+#flag -lwkhtmltox
+#include "wkhtmltox/pdf.h" # You can install the C package for your system from the wkhtmltopdf.org/downloads.html page
+struct C.wkhtmltopdf_global_settings {}
+
+struct C.wkhtmltopdf_object_settings {}
+
+struct C.wkhtmltopdf_converter {}
+
+fn C.wkhtmltopdf_init(use_graphics bool) int
+
+fn C.wkhtmltopdf_deinit() int
+
+fn C.wkhtmltopdf_version() charptr
+
+fn C.wkhtmltopdf_create_global_settings() &C.wkhtmltopdf_global_settings
+
+fn C.wkhtmltopdf_destroy_global_settings(global_settings &C.wkhtmltopdf_global_settings)
+
+fn wkhtmltopdf_set_global_setting(global_settings &C.wkhtmltopdf_global_settings, name charptr, value charptr) bool
+
+fn C.wkhtmltopdf_create_object_settings() &C.wkhtmltopdf_object_settings
+
+fn C.wkhtmltopdf_destroy_object_settings(object_settings &C.wkhtmltopdf_object_settings)
+
+fn C.wkhtmltopdf_set_object_setting(object_settings &C.wkhtmltopdf_object_settings, name charptr, value charptr) bool
+
+fn C.wkhtmltopdf_create_converter(global_settings &C.wkhtmltopdf_global_settings) &C.wkhtmltopdf_converter
+
+fn C.wkhtmltopdf_destroy_converter(converter &C.wkhtmltopdf_converter)
+
+fn C.wkhtmltopdf_add_object(converter &C.wkhtmltopdf_converter, object_settings &C.wkhtmltopdf_object_settings, data charptr)
+
+fn C.wkhtmltopdf_convert(converter &C.wkhtmltopdf_converter) bool
+
+fn C.wkhtmltopdf_http_error_code(converter &C.wkhtmltopdf_converter) int
+
+fn C.wkhtmltopdf_get_output(converter &C.wkhtmltopdf_converter, data &charptr) int
+
+fn main() {
+	// init
+	init := C.wkhtmltopdf_init(0)
+	println('wkhtmltopdf_init: $init')
+	version := C.wkhtmltopdf_version()
+	println('wkhtmltopdf_version: $version')
+	global_settings := C.wkhtmltopdf_create_global_settings()
+	println('wkhtmltopdf_create_global_settings: ${voidptr(global_settings)}')
+	object_settings := C.wkhtmltopdf_create_object_settings()
+	println('wkhtmltopdf_create_object_settings')
+	converter := C.wkhtmltopdf_create_converter(global_settings)
+	println('wkhtmltopdf_create_converter: ${voidptr(converter)}')
+	// convert
+	mut result := C.wkhtmltopdf_set_object_setting(object_settings, 'page', 'http://www.google.com.br')
+	println('wkhtmltopdf_set_object_setting: $result [page = http://www.google.com.br]')
+	C.wkhtmltopdf_add_object(converter, object_settings, 0)
+	println('wkhtmltopdf_add_object')
+	result = C.wkhtmltopdf_convert(converter)
+	println('wkhtmltopdf_convert: $result')
+	error_code := C.wkhtmltopdf_http_error_code(converter)
+	println('wkhtmltopdf_http_error_code: $error_code')
+	if result {
+		data := &charptr(0)
+		size := C.wkhtmltopdf_get_output(converter, &data)
+		println('wkhtmltopdf_get_output: $size bytes')
+		mut file := os.open_file('./google.pdf', 'w+', 0o666) or {
+			println('ERR: $err')
+			return
+		}
+		wrote := file.write_bytes(data, size)
+		println('write_bytes: $wrote [./google.pdf]')
+		file.flush()
+		file.close()
+	}
+	// destroy
+	C.wkhtmltopdf_destroy_converter(converter)
+	println('wkhtmltopdf_destroy_converter')
+	C.wkhtmltopdf_destroy_object_settings(object_settings)
+	println('wkhtmltopdf_destroy_object_settings: ${voidptr(object_settings)}')
+	C.wkhtmltopdf_destroy_global_settings(global_settings)
+	println('wkhtmltopdf_destroy_global_settings')
+	deinit := C.wkhtmltopdf_deinit()
+	println('wkhtmltopdf_deinit: $deinit')
+}