api: create QR codes from any data

deltachat-ffi/deltachat.h

@@ -2611,6 +2611,7 @@ char*           dc_get_securejoin_qr         (dc_context_t* context, uint32_t ch
  * Get QR code image from the QR code text generated by dc_get_securejoin_qr().
  * See dc_get_securejoin_qr() for details about the contained QR code.
  *
+ * @deprecated 2024-10 use dc_create_qr_svg(dc_get_securejoin_qr()) instead.
  * @memberof dc_context_t
  * @param context The context object.
  * @param chat_id group-chat-id for secure-join or 0 for setup-contact,
@@ -2791,6 +2792,22 @@ dc_array_t* dc_get_locations                (dc_context_t* context, uint32_t cha
 void        dc_delete_all_locations         (dc_context_t* context);
 
 
+// misc
+
+/**
+ * Create a QR code from any input data.
+ *
+ * The QR code is returned as a square SVG image.
+ *
+ * @memberof dc_context_t
+ * @param payload The content for the QR code.
+ * @return SVG image with the QR code.
+ *     On errors, an empty string is returned.
+ *     The returned string must be released using dc_str_unref() after usage.
+ */
+char*           dc_create_qr_svg             (const char* payload);
+
+
 /**
  * Get last error string.
  *
@@ -2879,6 +2896,7 @@ char* dc_backup_provider_get_qr (const dc_backup_provider_t* backup_provider);
  * This works like dc_backup_provider_qr() but returns the text of a rendered
  * SVG image containing the QR code.
  *
+ * @deprecated 2024-10 use dc_create_qr_svg(dc_backup_provider_get_qr()) instead.
  * @memberof dc_backup_provider_t
  * @param backup_provider The backup provider object as created by
  *    dc_backup_provider_new().
@@ -2918,7 +2936,7 @@ void dc_backup_provider_unref (dc_backup_provider_t* backup_provider);
  * Gets a backup offered by a dc_backup_provider_t object on another device.
  *
  * This function is called on a device that scanned the QR code offered by
- * dc_backup_sender_qr() or dc_backup_sender_qr_svg().  Typically this is a
+ * dc_backup_provider_get_qr().  Typically this is a
  * different device than that which provides the backup.
  *
  * This call will block while the backup is being transferred and only

deltachat-ffi/src/lib.rs

@@ -30,7 +30,7 @@ use deltachat::ephemeral::Timer as EphemeralTimer;
 use deltachat::imex::BackupProvider;
 use deltachat::key::preconfigure_keypair;
 use deltachat::message::MsgId;
-use deltachat::qr_code_generator::{generate_backup_qr, get_securejoin_qr_svg};
+use deltachat::qr_code_generator::{create_qr_svg, generate_backup_qr, get_securejoin_qr_svg};
 use deltachat::stock_str::StockMessage;
 use deltachat::webxdc::StatusUpdateSerial;
 use deltachat::*;
@@ -2594,6 +2594,18 @@ pub unsafe extern "C" fn dc_delete_all_locations(context: *mut dc_context_t) {
     });
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_create_qr_svg(payload: *const libc::c_char) -> *mut libc::c_char {
+    if payload.is_null() {
+        eprintln!("ignoring careless call to dc_create_qr_svg()");
+        return "".strdup();
+    }
+
+    create_qr_svg(&to_string_lossy(payload))
+        .unwrap_or_else(|_| "".to_string())
+        .strdup()
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_get_last_error(context: *mut dc_context_t) -> *mut libc::c_char {
     if context.is_null() {

deltachat-repl/src/cmdline.rs

@@ -22,6 +22,7 @@ use deltachat::mimeparser::SystemMessage;
 use deltachat::peer_channels::{send_webxdc_realtime_advertisement, send_webxdc_realtime_data};
 use deltachat::peerstate::*;
 use deltachat::qr::*;
+use deltachat::qr_code_generator::create_qr_svg;
 use deltachat::reaction::send_reaction;
 use deltachat::receive_imf::*;
 use deltachat::sql;
@@ -425,6 +426,7 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
                  checkqr <qr-content>\n\
                  joinqr <qr-content>\n\
                  setqr <qr-content>\n\
+                 createqrsvg <qr-content>\n\
                  providerinfo <addr>\n\
                  fileinfo <file>\n\
                  estimatedeletion <seconds>\n\
@@ -1249,6 +1251,13 @@ pub async fn cmdline(context: Context, line: &str, chat_id: &mut ChatId) -> Resu
                 Err(err) => println!("Cannot set config from QR code: {err:?}"),
             }
         }
+        "createqrsvg" => {
+            ensure!(!arg1.is_empty(), "Argument <qr-content> missing.");
+            let svg = create_qr_svg(arg1)?;
+            let file = dirs::home_dir().unwrap_or_default().join("qr.svg");
+            fs::write(&file, svg).await?;
+            println!("{file:#?} written.");
+        }
         "providerinfo" => {
             ensure!(!arg1.is_empty(), "Argument <addr> missing.");
             let proxy_enabled = context

deltachat-repl/src/main.rs

@@ -240,12 +240,13 @@ const CONTACT_COMMANDS: [&str; 9] = [
     "unblock",
     "listblocked",
 ];
-const MISC_COMMANDS: [&str; 11] = [
+const MISC_COMMANDS: [&str; 12] = [
     "getqr",
     "getqrsvg",
     "getbadqr",
     "checkqr",
     "joinqr",
+    "createqrsvg",
     "fileinfo",
     "clear",
     "exit",

src/qr_code_generator.rs

@@ -14,6 +14,65 @@ use crate::qr::{self, Qr};
 use crate::securejoin;
 use crate::stock_str::{self, backup_transfer_qr};
 
+/// Create a QR code from any input data.
+pub fn create_qr_svg(qrcode_content: &str) -> Result<String> {
+    let all_size = 512.0;
+    let qr_code_size = 416.0;
+
+    let qr = QrCode::encode_text(qrcode_content, QrCodeEcc::Medium)?;
+    let mut svg = String::with_capacity(28000);
+    let mut w = tagger::new(&mut svg);
+
+    w.elem("svg", |d| {
+        d.attr("xmlns", "http://www.w3.org/2000/svg")?;
+        d.attr("viewBox", format_args!("0 0 {all_size} {all_size}"))?;
+        d.attr("xmlns:xlink", "http://www.w3.org/1999/xlink")?; // required for enabling xlink:href on browsers
+        Ok(())
+    })?
+    .build(|w| {
+        // background
+        w.single("rect", |d| {
+            d.attr("x", 0)?;
+            d.attr("y", 0)?;
+            d.attr("width", all_size)?;
+            d.attr("height", all_size)?;
+            d.attr("style", "fill:#ffffff")?;
+            Ok(())
+        })?;
+        // QR code
+        w.elem("g", |d| {
+            d.attr(
+                "transform",
+                format!(
+                    "translate({},{})",
+                    (all_size - qr_code_size) / 2.0,
+                    ((all_size - qr_code_size) / 2.0)
+                ),
+            )
+        })?
+        .build(|w| {
+            w.single("path", |d| {
+                let mut path_data = String::with_capacity(0);
+                let scale = qr_code_size / qr.size() as f32;
+
+                for y in 0..qr.size() {
+                    for x in 0..qr.size() {
+                        if qr.get_module(x, y) {
+                            path_data += &format!("M{x},{y}h1v1h-1z");
+                        }
+                    }
+                }
+
+                d.attr("style", "fill:#000000")?;
+                d.attr("d", path_data)?;
+                d.attr("transform", format!("scale({scale})"))
+            })
+        })
+    })?;
+
+    Ok(svg)
+}
+
 /// Returns SVG of the QR code to join the group or verify contact.
 ///
 /// If `chat_id` is `None`, returns verification QR code.
@@ -304,6 +363,14 @@ mod tests {
 
     use super::*;
 
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_create_qr_svg() -> Result<()> {
+        let svg = create_qr_svg("this is a test QR code \" < > &")?;
+        assert!(svg.contains("<svg"));
+        assert!(svg.contains("</svg>"));
+        Ok(())
+    }
+
     #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
     async fn test_svg_escaping() {
         let svg = inner_generate_secure_join_qr_code(