More progress on INCR

v2/claim.go

@@ -9,25 +9,33 @@ import "github.com/jezek/xgbutil/xprop"
 import "github.com/jezek/xgbutil/xevent"
 import "github.com/jezek/xgbutil/xwindow"
 
-const format8bit  byte = 8
-const format16bit byte = 16
-const format32bit byte = 32
+const format8bit       byte = 8
+const format16bit      byte = 16
+const format32bit      byte = 32
+const propertyNewValue byte = 0
+const propertyDelete   byte = 1
 
 type claimRequest struct {
 	reader io.ReadSeekCloser
-	ty     xproto.Atom // must be "INCR"
+	ty     xproto.Atom
 	event  xevent.SelectionRequestEvent
 }
 
+type claimRequestKey struct {
+	property  xproto.Atom
+	requestor xproto.Window
+}
+
 // Claim represents a claim that a window has on a particular selection.
 type Claim struct {
+	open      bool
+	incr      bool
 	window    *xwindow.Window
 	data      Data
 	selection xproto.Atom
 	timestamp xproto.Timestamp
-	open      bool
 
-	requests map[xproto.Atom] claimRequest
+	requests map[claimRequestKey] *claimRequest
 }
 
 // NewClaim claims ownership of a specified selection, and allows using data
@@ -65,11 +73,12 @@ func NewClaim (window *xwindow.Window, selection xproto.Atom, data Data, timesta
 
 	return &Claim {
 		open:      true,
+		incr:      false, // TODO change to enable INCR
 		window:    window,
 		data:      data,
 		selection: selection,
 		timestamp: timestamp,
-		requests:  make(map[xproto.Atom] claimRequest),
+		requests:  make(map[claimRequestKey] *claimRequest),
 	}, nil
 }
 
@@ -101,12 +110,10 @@ func (claim *Claim) fulfillSelectionRequest (
 	// property on the requestor window and should set the property's type
 	// to some appropriate value, which need not be the same as the
 	// specified target.
-	err := xproto.ChangePropertyChecked (
-		claim.window.X.Conn(),
+	err := claim.changePropertyChecked (
 		xproto.PropModeReplace, request.Requestor,
 		request.Property,
-		ty, format,
-		uint32(len(data) / (int(format) / 8)), data).Check()
+		ty, format, data)
 	if err != nil { die() }
 
 	// If the property is successfully stored, the owner should acknowledge
@@ -124,6 +131,19 @@ func (claim *Claim) fulfillSelectionRequest (
 		false, request.Requestor, 0, string(event))
 }
 
+func (claim *Claim) changePropertyChecked (
+	mode     byte,
+	window   xproto.Window,
+	property xproto.Atom,
+	ty       xproto.Atom,
+	format   byte,
+	data     []byte,
+) error {
+	return xproto.ChangePropertyChecked (
+		claim.window.X.Conn(), mode, window, property, ty, format,
+		uint32(len(data) / (int(format) / 8)), data).Check()
+}
+
 // While the selection claim is active, HandleSelectionRequest should be called
 // when the owner window recieves a SelectionRequest event. This must be
 // registered as an event handler manually.
@@ -185,14 +205,52 @@ func (claim *Claim) HandleSelectionRequest (
 		claim.fulfillSelectionRequest(data, format32bit, atomAtom, event)
 
 	default:
+		incr, err := xprop.Atm(claim.window.X, "INCR")
+		if err != nil { die(); return }
+	
 		// respond with data
 		reader, ok := claim.data.Convert(Target(targetName))
 		if !ok { die(); return }
-		reader.Seek(0, io.SeekStart)
-		data, err := io.ReadAll(reader)
-		reader.Close()
-		if err != nil { die() }
-		claim.fulfillSelectionRequest(data, format8bit, event.Target, event)
+
+		if claim.incr {
+			// TODO: we need to subscribe to PropertyNotify events
+			// on the destination window. apparently event masks as
+			// set by ChangeWindowAttributes are client-specific.
+			// we also need to clean up afterwards.
+			// https://tronche.com/gui/x/xlib/window/XChangeWindowAttributes.html
+			
+			request := &claimRequest {
+				reader: reader,
+				ty:     event.Target,
+				event:  event,
+			}
+
+			// Requestors may receive a property of type INCR in
+			// response to any target that results in selection
+			// data. This indicates that the owner will send the
+			// actual data incrementally. The contents of the INCR
+			// property will be an integer, which represents a lower
+			// bound on the number of bytes of data in the
+			// selection.
+
+			data := [4]byte { }
+			xgb.Put32(data[:], 1)
+			err := claim.changePropertyChecked (
+				xproto.PropModeReplace, event.Requestor,
+				event.Property, incr, format32bit, data[:])
+			if err != nil { die() }
+
+			claim.requests[claimRequestKey {
+				property:  event.Property,
+				requestor: event.Requestor,
+			}] = request
+		} else {
+			reader.Seek(0, io.SeekStart)
+			data, err := io.ReadAll(reader)
+			reader.Close()
+			if err != nil { die() }
+			claim.fulfillSelectionRequest(data, format8bit, event.Target, event)
+		}
 	}
 }
 
@@ -203,21 +261,28 @@ func (claim *Claim) HandlePropertyNotify (
 	connection *xgbutil.XUtil,
 	event xevent.PropertyNotifyEvent,
 ) {
+	// The selection requestor starts the transfer process by deleting the
+	// (type==INCR) property forming the reply to the selection.
+	// 
 	// The selection owner then:
 	// ... Waits between each append for a PropertyNotify (state==Deleted)
 	// event that shows that the requestor has read the data. The reason for
 	// doing this is to limit the consumption of space in the server.
+	if event.State != propertyDelete { return }
 
-	// FIXME check for state==Deleted
 	// if the request does not exist, the property was either modified in
 	// error or the request has already finished. either way, we simply
 	// exit.
-	request, ok := claim.requests[event.Atom]
+	key := claimRequestKey {
+		property:  event.Atom,
+		requestor: event.Window,
+	}
+	request, ok := claim.requests[key]
 	if !ok { return }
 
 	done := func () {
 		request.reader.Close()
-		delete(claim.requests, request.event.Property)
+		delete(claim.requests, key)
 	}
 	
 	die := func () {
@@ -238,13 +303,10 @@ func (claim *Claim) HandlePropertyNotify (
 		// the same window as the selection reply with a type corresponding to
 		// the actual type of the converted selection. The size should be less
 		// than the maximum-request-size in the connection handshake.
-		format := format8bit
-		err = xproto.ChangePropertyChecked (
-			claim.window.X.Conn(),
-			xproto.PropModeAppend, request.event.Requestor,
-			request.event.Property,
-			request.ty, format,
-			uint32(len(dataRead) / (int(format) / 8)), dataRead).Check()
+		err := claim.changePropertyChecked (
+			xproto.PropModeReplace,
+			request.event.Requestor, request.event.Property,
+			request.ty, format8bit, dataRead)
 		if err != nil { die(); return }
 		
 	} else {
@@ -254,14 +316,10 @@ func (claim *Claim) HandlePropertyNotify (
 		// server) until a PropertyNotify (state==Deleted) event that
 		// shows that the data has been read by the requestor and then
 		// writes zero-length data to the property.
-
-		format := format8bit
-		err := xproto.ChangePropertyChecked (
-			claim.window.X.Conn(),
-			xproto.PropModeAppend, request.event.Requestor,
-			request.event.Property,
-			request.ty, format,
-			0, nil).Check()
+		err := claim.changePropertyChecked (
+			xproto.PropModeReplace,
+			request.event.Requestor, request.event.Property,
+			request.ty, format8bit, nil)
 		if err != nil { die(); return }
 
 		done()