From 8e23b5b70d8622784e4856e5f14493a8893eab8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Mon, 26 Oct 2020 21:02:53 +0100
Subject: [PATCH] selection: implement support for drag-and-drop
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We accept COPY and MOVE actions, for text/plain;charset=utf-8
mime-types.

To implement DnD, we need to track the current DnD data offer *and*
the terminal instance it is (currently) targeting.

To do this, a seat has a new member, ‘dnd_term’. On a DnD enter event,
we lookup the corresponding terminal instance and point ‘dnd_term’ to
it.

On a DnD leave event, ‘dnd_term’ is reset.

The DnD data offer is tracked in the terminal’s wayland window
instance. It is reset, along with the seat’s ‘dnd_term’ on a DnD leave
event.

On a drop event, we immediately clear the seat’s ‘dnd_term’, to ensure
we don’t reset it, or destroy the offer before the drop has been
completed.

The drop’s ‘done()’ callback takes care of destroying and resetting
the DnD offer in the terminal’s wayland window instance.

Closes #175
---
 CHANGELOG.md |  2 ++
 selection.c  | 96 +++++++++++++++++++++++++++++++++++++++++++++++++---
 wayland.h    |  5 +++
 3 files changed, 98 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a0cb347f..fdb6d97d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,8 @@
   `foot.ini`. These options allow custom bold/italic fonts. They are
   unset by default, meaning the bold/italic version of the regular
   font is used (https://codeberg.org/dnkl/foot/issues/169).
+* Drag & drop support; text, files and URLs can now be dropped in a
+  foot terminal window (https://codeberg.org/dnkl/foot/issues/175).
 
 
 ### Changed
diff --git a/selection.c b/selection.c
index c76a1608..278a892b 100644
--- a/selection.c
+++ b/selection.c
@@ -898,7 +898,7 @@ selection_stop_scroll_timer(struct terminal *term)
 static void
 target(void *data, struct wl_data_source *wl_data_source, const char *mime_type)
 {
-    LOG_WARN("TARGET: mime-type=%s", mime_type);
+    LOG_DBG("TARGET: mime-type=%s", mime_type);
 }
 
 struct clipboard_send {
@@ -1008,19 +1008,23 @@ cancelled(void *data, struct wl_data_source *wl_data_source)
     clipboard->text = NULL;
 }
 
+/* We don’t support dragging *from* */
 static void
 dnd_drop_performed(void *data, struct wl_data_source *wl_data_source)
 {
+    //LOG_DBG("DnD drop performed");
 }
 
 static void
 dnd_finished(void *data, struct wl_data_source *wl_data_source)
 {
+    //LOG_DBG("DnD finished");
 }
 
 static void
 action(void *data, struct wl_data_source *wl_data_source, uint32_t dnd_action)
 {
+    //LOG_DBG("DnD action: %u", dnd_action);
 }
 
 static const struct wl_data_source_listener data_source_listener = {
@@ -1464,17 +1468,20 @@ selection_from_primary(struct seat *seat, struct terminal *term)
 static void
 offer(void *data, struct wl_data_offer *wl_data_offer, const char *mime_type)
 {
+    LOG_INFO("OFFER: %s", mime_type);
 }
 
 static void
 source_actions(void *data, struct wl_data_offer *wl_data_offer,
                 uint32_t source_actions)
 {
+    LOG_INFO("ACTIONS: 0x%08x", source_actions);
 }
 
 static void
 offer_action(void *data, struct wl_data_offer *wl_data_offer, uint32_t dnd_action)
 {
+    LOG_INFO("OFFER ACTION: 0x%08x", dnd_action);
 }
 
 static const struct wl_data_offer_listener data_offer_listener = {
@@ -1488,6 +1495,7 @@ static void
 data_offer(void *data, struct wl_data_device *wl_data_device,
            struct wl_data_offer *id)
 {
+    //wl_data_offer_add_listener(id, &data_offer_listener, data);
 }
 
 static void
@@ -1495,11 +1503,43 @@ enter(void *data, struct wl_data_device *wl_data_device, uint32_t serial,
       struct wl_surface *surface, wl_fixed_t x, wl_fixed_t y,
       struct wl_data_offer *id)
 {
+    struct seat *seat = data;
+    struct wayland *wayl = seat->wayl;
+
+    assert(seat->dnd_term == NULL);
+
+    /* Remember current DnD offer */
+
+    /* Remmeber _which_ terminal the current DnD offer is targetting */
+    tll_foreach(wayl->terms, it) {
+        if (term_surface_kind(it->item, surface) == TERM_SURF_GRID &&
+            !it->item->is_sending_paste_data)
+        {
+            wl_data_offer_accept(id, serial, "text/plain;charset=utf-8");
+            wl_data_offer_set_actions(
+                id,
+                WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY | WL_DATA_DEVICE_MANAGER_DND_ACTION_MOVE,
+                WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY);
+
+            seat->dnd_term = it->item;
+            seat->dnd_term->window->dnd_offer = id;
+            return;
+        }
+    }
+
+    /* Either terminal is alraedy busy sending paste data, or mouse
+     * pointer isn’t over the grid */
+    seat->dnd_term = NULL;
+    wl_data_offer_set_actions(id, 0, WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY);
 }
 
 static void
 leave(void *data, struct wl_data_device *wl_data_device)
 {
+    struct seat *seat = data;
+    if (seat->dnd_term != NULL)
+        seat->dnd_term->window->dnd_offer = NULL;
+    seat->dnd_term = NULL;
 }
 
 static void
@@ -1508,9 +1548,59 @@ motion(void *data, struct wl_data_device *wl_data_device, uint32_t time,
 {
 }
 
+static void
+dnd_done(void *user)
+{
+    struct terminal *term = user;
+    struct wl_data_offer *offer = term->window->dnd_offer;
+
+    assert(offer != NULL);
+    term->window->dnd_offer = NULL;
+
+    wl_data_offer_finish(offer);
+    wl_data_offer_destroy(offer);
+
+    from_clipboard_done(user);
+}
+
 static void
 drop(void *data, struct wl_data_device *wl_data_device)
 {
+    struct seat *seat = data;
+
+    struct terminal *term = seat->dnd_term;
+    assert(term != NULL);
+
+    struct wl_data_offer *offer = term->window->dnd_offer;
+    assert(offer != NULL);
+    seat->dnd_term = NULL;
+
+    /* Prepare a pipe the other client can write its selection to us */
+    int fds[2];
+    if (pipe2(fds, O_CLOEXEC) == -1) {
+        LOG_ERRNO("failed to create pipe");
+        goto err;
+    }
+
+    int read_fd = fds[0];
+    int write_fd = fds[1];
+
+    /* Give write-end of pipe to other client */
+    wl_data_offer_receive(offer, "text/plain;charset=utf-8", write_fd);
+
+    /* Don't keep our copy of the write-end open (or we'll never get EOF) */
+    close(write_fd);
+
+    term->is_sending_paste_data = true;
+
+    if (term->bracketed_paste)
+        term_paste_data_to_slave(term, "\033[200~", 6);
+
+    begin_receive_clipboard(term, read_fd, &from_clipboard_cb, &dnd_done, term);
+    return;
+
+err:
+    wl_data_offer_destroy(offer);
 }
 
 static void
@@ -1526,10 +1616,6 @@ selection(void *data, struct wl_data_device *wl_data_device,
         wl_data_offer_destroy(clipboard->data_offer);
 
     clipboard->data_offer = id;
-#if 0
-    if (id != NULL)
-        wl_data_offer_add_listener(id, &data_offer_listener, term);
-#endif
 }
 
 const struct wl_data_device_listener data_device_listener = {
diff --git a/wayland.h b/wayland.h
index 70c2098a..bf3db76c 100644
--- a/wayland.h
+++ b/wayland.h
@@ -205,6 +205,9 @@ struct seat {
 
     struct wl_clipboard clipboard;
     struct wl_primary primary;
+
+    /* Drag ‘n’ drop */
+    struct terminal *dnd_term;
 };
 
 enum csd_surface {
@@ -309,6 +312,8 @@ struct wl_window {
 
     struct wl_callback *frame_callback;
 
+    struct wl_data_offer *dnd_offer;
+
     tll(const struct monitor *) on_outputs; /* Outputs we're mapped on */
 
     bool is_configured;