seems like i have found solution how to properly render buttons

ui/models/messagefeed.cpp

@@ -31,6 +31,7 @@ const QHash<int, QByteArray> Models::MessageFeed::roles = {
     {SentByMe,"sentByMe"},
     {Avatar, "avatar"},
     {Attach, "attach"},
+    {Id, "id"},
     {Bulk, "bulk"}
 };
 
@@ -94,8 +95,12 @@ QVariant Models::MessageFeed::data(const QModelIndex& index, int role) const
         
         switch (role) {
             case Qt::DisplayRole:
-            case Text: 
+            case Text: {
-                answer = msg->getBody();
+                QString body = msg->getBody();
+                if (body != msg->getOutOfBandUrl()) {
+                    answer = body;
+                }
+            }
                 break;
             case Sender: 
                 if (sentByMe(*msg)) {
@@ -143,13 +148,22 @@ QVariant Models::MessageFeed::data(const QModelIndex& index, int role) const
             case Attach: 
                 answer.setValue(fillAttach(*msg));
                 break;
+            case Id: 
+                answer.setValue(msg->getId());
+                break;
             case Bulk: {
                 FeedItem item;
+                item.id = msg->getId();
                 item.sentByMe = sentByMe(*msg);
                 item.date = msg->getTime();
                 item.state = msg->getState();
                 item.correction = msg->getEdited();
-                item.text = msg->getBody();
+                
+                QString body = msg->getBody();
+                if (body != msg->getOutOfBandUrl()) {
+                    item.text = body;
+                }
+                
                 item.avatar.clear();
                 if (item.sentByMe) {
                     item.sender = rosterItem->getAccountName();

ui/models/messagefeed.h

@@ -76,6 +76,7 @@ public:
         SentByMe,
         Avatar,
         Attach,
+        Id,
         Bulk
     };
     
@@ -146,6 +147,7 @@ struct Attachment {
 };
 
 struct FeedItem {
+    QString id;
     QString text;
     QString sender;
     QString avatar;

ui/utils/feedview.cpp

@@ -23,13 +23,17 @@
 #include <QScrollBar>
 #include <QDebug>
 
+#include "messagedelegate.h"
+
 constexpr int maxMessageHeight = 10000;
 constexpr int approximateSingleMessageHeight = 20;
 
 FeedView::FeedView(QWidget* parent):
     QAbstractItemView(parent),
     hints(),
-    vo(0)
+    vo(0),
+    specialDelegate(false),
+    clearWidgetsMode(false)
 {
     horizontalScrollBar()->setRange(0, 0);
     verticalScrollBar()->setSingleStep(approximateSingleMessageHeight);
@@ -163,6 +167,10 @@ void FeedView::updateGeometries()
         bar->setPageStep(layoutBounds.height());
         bar->setValue(previousOffset - layoutBounds.height() - vo);
     }
+    
+    if (specialDelegate) {
+        clearWidgetsMode = true;
+    }
 }
 
 bool FeedView::tryToCalculateGeometriesWithNoScrollbars(const QStyleOptionViewItem& option, const QAbstractItemModel* m, uint32_t totalHeight)
@@ -222,17 +230,32 @@ void FeedView::paintEvent(QPaintEvent* event)
     option.features = QStyleOptionViewItem::WrapText;
     QPoint cursor = vp->mapFromGlobal(QCursor::pos());
     
+    if (clearWidgetsMode && specialDelegate) {
+        MessageDelegate* del = dynamic_cast<MessageDelegate*>(itemDelegate());
+        del->beginClearWidgets();
+    }
+    
     for (const QModelIndex& index : toRener) {
         option.rect = visualRect(index);
         option.state.setFlag(QStyle::State_MouseOver, option.rect.contains(cursor));
         itemDelegate(index)->paint(&painter, option, index);
     }
+    
+    if (clearWidgetsMode && specialDelegate) {
+        MessageDelegate* del = dynamic_cast<MessageDelegate*>(itemDelegate());
+        del->endClearWidgets();
+        clearWidgetsMode = false;
+    }
 }
 
 void FeedView::verticalScrollbarValueChanged(int value)
 {
     vo = verticalScrollBar()->maximum() - value;
     
+    if (specialDelegate) {
+        clearWidgetsMode = true;
+    }
+    
     QAbstractItemView::verticalScrollbarValueChanged(vo);
 }
 
@@ -250,3 +273,15 @@ QFont FeedView::getFont() const
 {
     return viewOptions().font;
 }
+
+void FeedView::setItemDelegate(QAbstractItemDelegate* delegate)
+{
+    QAbstractItemView::setItemDelegate(delegate);
+    
+    MessageDelegate* del = dynamic_cast<MessageDelegate*>(delegate);
+    if (del) {
+        specialDelegate = true;
+    } else {
+        specialDelegate = false;
+    }
+}

ui/utils/feedview.h

@@ -42,6 +42,7 @@ public:
     QModelIndex moveCursor(QAbstractItemView::CursorAction cursorAction, Qt::KeyboardModifiers modifiers) override;
     void setSelection(const QRect & rect, QItemSelectionModel::SelectionFlags command) override;
     QRegion visualRegionForSelection(const QItemSelection & selection) const override;
+    void setItemDelegate(QAbstractItemDelegate* delegate);
     
     QFont getFont() const;
     
@@ -69,6 +70,8 @@ private:
     };
     std::deque<Hint> hints;
     int vo;
+    bool specialDelegate;
+    bool clearWidgetsMode;
     
 };
 

ui/utils/messagedelegate.cpp

@@ -19,6 +19,7 @@
 #include <QDebug>
 #include <QPainter>
 #include <QApplication>
+#include <QMouseEvent>
 
 #include "messagedelegate.h"
 #include "ui/models/messagefeed.h"
@@ -34,23 +35,23 @@ dateFont(),
 bodyMetrics(bodyFont),
 nickMetrics(nickFont),
 dateMetrics(dateFont),
-downloadButton(new QPushButton()),
+buttonHeight(0),
-uploadButton(new QPushButton())
+buttons(new std::map<QString, FeedButton*>()),
+idsToKeep(new std::set<QString>()),
+clearingWidgets(false)
 {
-    downloadButton->setText(tr("Download"));
+    QPushButton btn;
-    uploadButton->setText(tr("Retry"));
+    buttonHeight = btn.sizeHint().height();
-    
-    //this is done for the buttons to calculate their acual size for we are going to use them further
-    downloadButton->setAttribute(Qt::WA_DontShowOnScreen);
-    uploadButton->setAttribute(Qt::WA_DontShowOnScreen);
-    downloadButton->show();
-    uploadButton->show();
 }
 
 MessageDelegate::~MessageDelegate()
 {
-    delete uploadButton;
+    for (const std::pair<const QString, FeedButton*>& pair: *buttons){
-    delete downloadButton;
+        delete pair.second;
+    }
+    
+    delete idsToKeep;
+    delete buttons;
 }
 
 void MessageDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
@@ -85,7 +86,10 @@ void MessageDelegate::paint(QPainter* painter, const QStyleOptionViewItem& optio
     }
     opt.rect = messageRect;
     
-    QSize messageSize = bodyMetrics.boundingRect(messageRect, Qt::TextWordWrap, data.text).size();
+    QSize messageSize(0, 0);
+    if (data.text.size() > 0) {
+        messageSize = bodyMetrics.boundingRect(messageRect, Qt::TextWordWrap, data.text).size();
+    }
     messageSize.rheight() += nickMetrics.lineSpacing();
     messageSize.rheight() += dateMetrics.height();
     if (messageSize.width() < opt.rect.width()) {
@@ -111,32 +115,19 @@ void MessageDelegate::paint(QPainter* painter, const QStyleOptionViewItem& optio
         case Models::downloading:
             break;
         case Models::remote:
-            if (data.sentByMe) {
-                painter->translate(option.rect.width() - avatarHeight - margin * 2 - downloadButton->width(), opt.rect.top());
-            } else {
-                painter->translate(opt.rect.topLeft());
-            }
-            downloadButton->render(painter, QPoint(), QRegion(), QWidget::DrawChildren);
-            opt.rect.adjust(0, downloadButton->height(), 0, 0);
-            break;
         case Models::local:
-            if (data.sentByMe) {
+            paintButton(getButton(data), painter, data.sentByMe, opt);
-                painter->translate(option.rect.width() - avatarHeight - margin * 2 - uploadButton->width(), opt.rect.top());
-            } else {
-                painter->translate(opt.rect.topLeft());
-            }
-            uploadButton->render(painter, QPoint(), QRegion(), QWidget::DrawChildren);
-            opt.rect.adjust(0, uploadButton->height(), 0, 0);
             break;
         case Models::ready:
             break;
     }
     painter->restore();
     
+    if (data.text.size() > 0) {
         painter->setFont(bodyFont);
         painter->drawText(opt.rect, opt.displayAlignment | Qt::TextWordWrap, data.text, &rect);
-    
         opt.rect.adjust(0, rect.height(), 0, 0);
+    }
     painter->setFont(dateFont);
     QColor q = painter->pen().color();
     q.setAlpha(180);
@@ -144,6 +135,10 @@ void MessageDelegate::paint(QPainter* painter, const QStyleOptionViewItem& optio
     painter->drawText(opt.rect, opt.displayAlignment, data.date.toLocalTime().toString(), &rect);
     
     painter->restore();
+    
+    if (clearingWidgets) {
+        idsToKeep->insert(data.id);
+    }
 }
 
 QSize MessageDelegate::sizeHint(const QStyleOptionViewItem& option, const QModelIndex& index) const
@@ -153,7 +148,11 @@ QSize MessageDelegate::sizeHint(const QStyleOptionViewItem& option, const QModel
     opt.rect = messageRect;
     QVariant va = index.data(Models::MessageFeed::Attach);
     Models::Attachment attach = qvariant_cast<Models::Attachment>(va);
-    QSize messageSize = bodyMetrics.boundingRect(messageRect, Qt::TextWordWrap, index.data(Models::MessageFeed::Text).toString()).size();
+    QString body = index.data(Models::MessageFeed::Text).toString();
+    QSize messageSize(0, 0);
+    if (body.size() > 0) {
+        messageSize = bodyMetrics.boundingRect(messageRect, Qt::TextWordWrap, body).size();
+    }
     
     switch (attach.state) {
         case Models::none:
@@ -163,7 +162,7 @@ QSize MessageDelegate::sizeHint(const QStyleOptionViewItem& option, const QModel
             break;
         case Models::remote:
         case Models::local:
-            messageSize.rheight() += downloadButton->height();
+            messageSize.rheight() += buttonHeight;
             break;
         case Models::ready:
             break;
@@ -204,9 +203,88 @@ void MessageDelegate::initializeFonts(const QFont& font)
 bool MessageDelegate::editorEvent(QEvent* event, QAbstractItemModel* model, const QStyleOptionViewItem& option, const QModelIndex& index)
 {
     //qDebug() << event->type();
+    
+    
     return QStyledItemDelegate::editorEvent(event, model, option, index);
 }
 
+void MessageDelegate::paintButton(QPushButton* btn, QPainter* painter, bool sentByMe, QStyleOptionViewItem& option) const
+{
+    QPoint start;
+    if (sentByMe) {
+        start = {option.rect.width() - btn->width(), option.rect.top()};
+    } else {
+        start = option.rect.topLeft();
+    }
+    
+    QWidget* vp = static_cast<QWidget*>(painter->device());
+    btn->setParent(vp);
+    btn->move(start);
+    btn->show();
+    
+    option.rect.adjust(0, buttonHeight, 0, 0);
+}
+
+
+QPushButton * MessageDelegate::getButton(const Models::FeedItem& data) const
+{
+    std::map<QString, FeedButton*>::const_iterator itr = buttons->find(data.id);
+    FeedButton* result = 0;
+    if (itr != buttons->end()) {
+        if (
+            (data.attach.state == Models::remote && itr->second->download) ||
+            (data.attach.state == Models::local && !itr->second->download)
+        ) {
+            result = itr->second;
+        } else {
+            delete itr->second;
+            buttons->erase(itr);
+        }
+    }
+    
+    if (result == 0) {
+        result = new FeedButton();
+        result->messageId = data.id;
+        if (data.attach.state == Models::remote) {
+            result->setText(QCoreApplication::translate("MessageLine", "Download"));
+            result->download = true;
+        } else {
+            result->setText(QCoreApplication::translate("MessageLine", "Upload"));
+            result->download = false;
+        }
+        buttons->insert(std::make_pair(data.id, result));
+    }
+    
+    return result;
+}
+
+
+void MessageDelegate::beginClearWidgets()
+{
+    idsToKeep->clear();
+    clearingWidgets = true;
+}
+
+void MessageDelegate::endClearWidgets()
+{
+    if (clearingWidgets) {
+        std::set<QString> toRemove;
+        for (const std::pair<const QString, FeedButton*>& pair: *buttons){
+            if (idsToKeep->find(pair.first) == idsToKeep->end()) {
+                delete pair.second;
+                toRemove.insert(pair.first);
+            }
+        }
+        
+        for (const QString& key : toRemove) {
+            buttons->erase(key);
+        }
+        
+        idsToKeep->clear();
+        clearingWidgets = false;
+    }
+}
+
 
 // void MessageDelegate::setModelData(QWidget* editor, QAbstractItemModel* model, const QModelIndex& index) const
 // {

ui/utils/messagedelegate.h

@@ -19,13 +19,21 @@
 #ifndef MESSAGEDELEGATE_H
 #define MESSAGEDELEGATE_H
 
+#include <map>
+#include <set>
+
 #include <QStyledItemDelegate>
+#include <QStyleOptionButton>
 #include <QFont>
 #include <QFontMetrics>
 #include <QPushButton>
 
 #include "shared/icons.h"
 
+namespace Models {
+    struct FeedItem;
+};
+
 class MessageDelegate : public QStyledItemDelegate
 {
     Q_OBJECT
@@ -39,8 +47,20 @@ public:
     
     void initializeFonts(const QFont& font);
     bool editorEvent(QEvent * event, QAbstractItemModel * model, const QStyleOptionViewItem & option, const QModelIndex & index) override;
+    void endClearWidgets();
+    void beginClearWidgets();
+    
+protected:
+    void paintButton(QPushButton* btn, QPainter* painter, bool sentByMe, QStyleOptionViewItem& option) const;
+    QPushButton* getButton(const Models::FeedItem& data) const;
     
 private:
+    class FeedButton : public QPushButton {
+    public:
+        QString messageId;
+        bool download;
+    };
+    
     QFont bodyFont;
     QFont nickFont;
     QFont dateFont;
@@ -48,8 +68,11 @@ private:
     QFontMetrics nickMetrics;
     QFontMetrics dateMetrics;
     
-    QPushButton* downloadButton;
+    int buttonHeight;
-    QPushButton* uploadButton;
+    
+    std::map<QString, FeedButton*>* buttons;
+    std::set<QString>* idsToKeep;
+    bool clearingWidgets;
 };
 
 #endif // MESSAGEDELEGATE_H

ui/widgets/conversation.cpp

@@ -46,7 +46,7 @@ Conversation::Conversation(bool muc, Models::Account* acc, Models::Element* el,
     overlay(new QWidget()),
     filesToAttach(),
     feed(new FeedView()),
-    delegate(new MessageDelegate()),
+    delegate(new MessageDelegate(this)),
     scroll(down),
     manualSliderChange(false),
     requestingHistory(false),