Merge branch 'master' into q3k/clickity

1 files changed, 151 insertions, 349 deletions

diff --git a/gui/fpgaviewwidget.cc b/gui/fpgaviewwidget.cc
index 7ee2b4f9..ed3a0bce 100644
--- a/gui/fpgaviewwidget.cc
+++ b/gui/fpgaviewwidget.cc
@@ -31,220 +31,11 @@
 
 NEXTPNR_NAMESPACE_BEGIN
 
-void PolyLine::buildPoint(LineShaderData *building, const QVector2D *prev, const QVector2D *cur,
-                          const QVector2D *next) const
-{
-    // buildPoint emits two vertices per line point, along with normals to move
-    // them the right directio when rendering and miter to compensate for
-    // bends.
-
-    if (cur == nullptr) {
-        // BUG
-        return;
-    }
-
-    if (prev == nullptr && next == nullptr) {
-        // BUG
-        return;
-    }
-
-    // TODO(q3k): fast path for vertical/horizontal lines?
-
-    // TODO(q3k): consider moving some of the linear algebra to the GPU,
-    // they're better at this than poor old CPUs.
-
-    // Build two unit vectors pointing in the direction of the two segments
-    // defined by (prev, cur) and (cur, next)
-    QVector2D dprev, dnext;
-    if (prev == nullptr) {
-        dnext = *next - *cur;
-        dprev = dnext;
-    } else if (next == nullptr) {
-        dprev = *cur - *prev;
-        dnext = dprev;
-    } else {
-        dprev = *cur - *prev;
-        dnext = *next - *cur;
-    }
-    dprev.normalize();
-    dnext.normalize();
-
-    // Calculate tangent unit vector.
-    QVector2D tangent(dprev + dnext);
-    tangent.normalize();
-
-    // Calculate normal to tangent - this is the line on which the vectors need
-    // to be pushed to build a thickened line.
-    const QVector2D tangent_normal = QVector2D(-tangent.y(), tangent.x());
-
-    // Calculate normal to one of the lines.
-    const QVector2D dprev_normal = QVector2D(-dprev.y(), dprev.x());
-    // https://people.eecs.berkeley.edu/~sequin/CS184/IMGS/Sweep_PolyLine.jpg
-    // (the ^-1 is performed in the shader)
-    const float miter = QVector2D::dotProduct(tangent_normal, dprev_normal);
-
-    const float x = cur->x();
-    const float y = cur->y();
-    const float mx = tangent_normal.x();
-    const float my = tangent_normal.y();
-
-    // Push back 'left' vertex.
-    building->vertices.push_back(Vertex2DPOD(x, y));
-    building->normals.push_back(Vertex2DPOD(mx, my));
-    building->miters.push_back(miter);
-
-    // Push back 'right' vertex.
-    building->vertices.push_back(Vertex2DPOD(x, y));
-    building->normals.push_back(Vertex2DPOD(mx, my));
-    building->miters.push_back(-miter);
-}
-
-void PolyLine::build(LineShaderData &target) const
-{
-    if (points_.size() < 2) {
-        return;
-    }
-    const QVector2D *first = &points_.front();
-    const QVector2D *last = &points_.back();
-
-    // Index number of vertices, used to build the index buffer.
-    unsigned int startIndex = target.vertices.size();
-    unsigned int index = startIndex;
-
-    // For every point on the line, call buildPoint with (prev, point, next).
-    // If we're building a closed line, prev/next wrap around. Otherwise
-    // they are passed as nullptr and buildPoint interprets that accordinglu.
-    const QVector2D *prev = nullptr;
-
-    // Loop iterator used to ensure next is valid.
-    unsigned int i = 0;
-    for (const QVector2D &point : points_) {
-        const QVector2D *next = nullptr;
-        if (++i < points_.size()) {
-            next = (&point + 1);
-        }
-
-        // If the line is closed, wrap around. Otherwise, pass nullptr.
-        if (prev == nullptr && closed_) {
-            buildPoint(&target, last, &point, next);
-        } else if (next == nullptr && closed_) {
-            buildPoint(&target, prev, &point, first);
-        } else {
-            buildPoint(&target, prev, &point, next);
-        }
-
-        // If we have a prev point relative to cur, build a pair of triangles
-        // to render vertices into lines.
-        if (prev != nullptr) {
-            target.indices.push_back(index);
-            target.indices.push_back(index + 1);
-            target.indices.push_back(index + 2);
-
-            target.indices.push_back(index + 2);
-            target.indices.push_back(index + 1);
-            target.indices.push_back(index + 3);
-
-            index += 2;
-        }
-        prev = &point;
-    }
-
-    // If we're closed, build two more vertices that loop the line around.
-    if (closed_) {
-        target.indices.push_back(index);
-        target.indices.push_back(index + 1);
-        target.indices.push_back(startIndex);
-
-        target.indices.push_back(startIndex);
-        target.indices.push_back(index + 1);
-        target.indices.push_back(startIndex + 1);
-    }
-}
-
-bool LineShader::compile(void)
-{
-    program_ = new QOpenGLShaderProgram(parent_);
-    program_->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource_);
-    program_->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource_);
-    if (!program_->link()) {
-        printf("could not link program: %s\n", program_->log().toStdString().c_str());
-        return false;
-    }
-
-    if (!vao_.create())
-        log_abort();
-    vao_.bind();
-
-    if (!buffers_.position.create())
-        log_abort();
-    if (!buffers_.normal.create())
-        log_abort();
-    if (!buffers_.miter.create())
-        log_abort();
-    if (!buffers_.index.create())
-        log_abort();
-
-    attributes_.position = program_->attributeLocation("position");
-    attributes_.normal = program_->attributeLocation("normal");
-    attributes_.miter = program_->attributeLocation("miter");
-    uniforms_.thickness = program_->uniformLocation("thickness");
-    uniforms_.projection = program_->uniformLocation("projection");
-    uniforms_.color = program_->uniformLocation("color");
-
-    vao_.release();
-    return true;
-}
-
-void LineShader::draw(const LineShaderData &line, const QColor &color, float thickness, const QMatrix4x4 &projection)
-{
-    auto gl = QOpenGLContext::currentContext()->functions();
-    if (line.vertices.size() == 0)
-        return;
-    vao_.bind();
-    program_->bind();
-
-    buffers_.position.bind();
-    buffers_.position.allocate(&line.vertices[0], sizeof(Vertex2DPOD) * line.vertices.size());
-
-    buffers_.normal.bind();
-    buffers_.normal.allocate(&line.normals[0], sizeof(Vertex2DPOD) * line.normals.size());
-
-    buffers_.miter.bind();
-    buffers_.miter.allocate(&line.miters[0], sizeof(GLfloat) * line.miters.size());
-
-    buffers_.index.bind();
-    buffers_.index.allocate(&line.indices[0], sizeof(GLuint) * line.indices.size());
-
-    program_->setUniformValue(uniforms_.projection, projection);
-    program_->setUniformValue(uniforms_.thickness, thickness);
-    program_->setUniformValue(uniforms_.color, color.redF(), color.greenF(), color.blueF(), color.alphaF());
-
-    buffers_.position.bind();
-    program_->enableAttributeArray("position");
-    gl->glVertexAttribPointer(attributes_.position, 2, GL_FLOAT, GL_FALSE, 0, (void *)0);
-
-    buffers_.normal.bind();
-    program_->enableAttributeArray("normal");
-    gl->glVertexAttribPointer(attributes_.normal, 2, GL_FLOAT, GL_FALSE, 0, (void *)0);
-
-    buffers_.miter.bind();
-    program_->enableAttributeArray("miter");
-    gl->glVertexAttribPointer(attributes_.miter, 1, GL_FLOAT, GL_FALSE, 0, (void *)0);
-
-    buffers_.index.bind();
-    gl->glDrawElements(GL_TRIANGLES, line.indices.size(), GL_UNSIGNED_INT, (void *)0);
-
-    program_->disableAttributeArray("miter");
-    program_->disableAttributeArray("normal");
-    program_->disableAttributeArray("position");
-
-    program_->release();
-    vao_.release();
-}
-
-FPGAViewWidget::FPGAViewWidget(QWidget *parent)
-        : QOpenGLWidget(parent), lineShader_(this), zoom_(500.f), ctx_(nullptr), paintTimer_(this),
-          rendererData_(new FPGAViewWidget::RendererData), rendererArgs_(new FPGAViewWidget::RendererArgs)
+FPGAViewWidget::FPGAViewWidget(QWidget *parent) :
+        QOpenGLWidget(parent), ctx_(nullptr), paintTimer_(this),
+        lineShader_(this), zoom_(500.0f),
+        rendererData_(new FPGAViewWidget::RendererData),
+        rendererArgs_(new FPGAViewWidget::RendererArgs)
 {
     colors_.background = QColor("#000000");
     colors_.grid = QColor("#333");
@@ -311,68 +102,49 @@ void FPGAViewWidget::initializeGL()
                  0.0);
 }
 
-void FPGAViewWidget::drawDecal(LineShaderData &out, const DecalXY &decal)
+void FPGAViewWidget::drawGraphicElement(LineShaderData &out, const GraphicElement &el, float x, float y)
 {
     const float scale = 1.0;
+
+    if (el.type == GraphicElement::TYPE_BOX) {
+        auto line = PolyLine(true);
+        line.point(x + scale * el.x1, y + scale * el.y1);
+        line.point(x + scale * el.x2, y + scale * el.y1);
+        line.point(x + scale * el.x2, y + scale * el.y2);
+        line.point(x + scale * el.x1, y + scale * el.y2);
+        line.build(out);
+    }
+
+    if (el.type == GraphicElement::TYPE_LINE || el.type == GraphicElement::TYPE_ARROW) {
+        PolyLine(x + scale * el.x1, y + scale * el.y1, x + scale * el.x2, y + scale * el.y2)
+            .build(out);
+    }
+}
+
+void FPGAViewWidget::drawDecal(LineShaderData &out, const DecalXY &decal)
+{
     float offsetX = decal.x;
     float offsetY = decal.y;
 
     for (auto &el : ctx_->getDecalGraphics(decal.decal)) {
-
-        if (el.type == GraphicElement::G_BOX) {
-            auto line = PolyLine(true);
-            line.point(offsetX + scale * el.x1, offsetY + scale * el.y1);
-            line.point(offsetX + scale * el.x2, offsetY + scale * el.y1);
-            line.point(offsetX + scale * el.x2, offsetY + scale * el.y2);
-            line.point(offsetX + scale * el.x1, offsetY + scale * el.y2);
-            line.build(out);
-        }
-
-        if (el.type == GraphicElement::G_LINE || el.type == GraphicElement::G_ARROW) {
-            PolyLine(offsetX + scale * el.x1, offsetY + scale * el.y1, offsetX + scale * el.x2, offsetY + scale * el.y2)
-                    .build(out);
-        }
+        drawGraphicElement(out, el, offsetX, offsetY);
     }
 }
 
-void FPGAViewWidget::drawDecal(LineShaderData out[], const DecalXY &decal)
+void FPGAViewWidget::drawArchDecal(LineShaderData out[GraphicElement::STYLE_MAX], const DecalXY &decal)
 {
-    const float scale = 1.0;
-    float offsetX = 0.0, offsetY = 0.0;
+    float offsetX = decal.x;
+    float offsetY = decal.y;
 
     for (auto &el : ctx_->getDecalGraphics(decal.decal)) {
-        offsetX = decal.x;
-        offsetY = decal.y;
-
-        if (el.type == GraphicElement::G_BOX) {
-            auto line = PolyLine(true);
-            line.point(offsetX + scale * el.x1, offsetY + scale * el.y1);
-            line.point(offsetX + scale * el.x2, offsetY + scale * el.y1);
-            line.point(offsetX + scale * el.x2, offsetY + scale * el.y2);
-            line.point(offsetX + scale * el.x1, offsetY + scale * el.y2);
-            switch (el.style) {
-            case GraphicElement::G_FRAME:
-            case GraphicElement::G_INACTIVE:
-            case GraphicElement::G_ACTIVE:
-                line.build(out[el.style]);
-                break;
-            default:
-                break;
-            }
-        }
-
-        if (el.type == GraphicElement::G_LINE || el.type == GraphicElement::G_ARROW) {
-            auto line = PolyLine(offsetX + scale * el.x1, offsetY + scale * el.y1, offsetX + scale * el.x2,
-                                 offsetY + scale * el.y2);
-            switch (el.style) {
-            case GraphicElement::G_FRAME:
-            case GraphicElement::G_INACTIVE:
-            case GraphicElement::G_ACTIVE:
-                line.build(out[el.style]);
-                break;
-            default:
-                break;
-            }
+        switch (el.style) {
+        case GraphicElement::STYLE_FRAME:
+        case GraphicElement::STYLE_INACTIVE:
+        case GraphicElement::STYLE_ACTIVE:
+            drawGraphicElement(out[el.style], el, offsetX, offsetY);
+            break;
+        default:
+            break;
         }
     }
 }
@@ -402,24 +174,28 @@ void FPGAViewWidget::paintGL()
     float thick1Px = mouseToWorldDimensions(1, 0).x();
     float thick11Px = mouseToWorldDimensions(1.1, 0).x();
 
-    // Draw grid.
+    // Render grid.
     auto grid = LineShaderData();
     for (float i = -100.0f; i < 100.0f; i += 1.0f) {
         PolyLine(-100.0f, i, 100.0f, i).build(grid);
         PolyLine(i, -100.0f, i, 100.0f).build(grid);
     }
+    // Draw grid.
     lineShader_.draw(grid, colors_.grid, thick1Px, matrix);
 
     rendererDataLock_.lock();
-    lineShader_.draw(rendererData_->decals[0], colors_.frame, thick11Px, matrix);
-    lineShader_.draw(rendererData_->decals[1], colors_.hidden, thick11Px, matrix);
-    lineShader_.draw(rendererData_->decals[2], colors_.inactive, thick11Px, matrix);
-    lineShader_.draw(rendererData_->decals[3], colors_.active, thick11Px, matrix);
 
+    // Render Arch graphics.
+    lineShader_.draw(rendererData_->gfxByStyle[GraphicElement::STYLE_FRAME], colors_.frame, thick11Px, matrix);
+    lineShader_.draw(rendererData_->gfxByStyle[GraphicElement::STYLE_HIDDEN], colors_.hidden, thick11Px, matrix);
+    lineShader_.draw(rendererData_->gfxByStyle[GraphicElement::STYLE_INACTIVE], colors_.inactive, thick11Px, matrix);
+    lineShader_.draw(rendererData_->gfxByStyle[GraphicElement::STYLE_ACTIVE], colors_.active, thick11Px, matrix);
+
+    // Draw highlighted items.
     for (int i = 0; i < 8; i++)
-        lineShader_.draw(rendererData_->highlighted[i], colors_.highlight[i], thick11Px, matrix);
+        lineShader_.draw(rendererData_->gfxHighlighted[i], colors_.highlight[i], thick11Px, matrix);
 
-    lineShader_.draw(rendererData_->selected, colors_.selected, thick11Px, matrix);
+    lineShader_.draw(rendererData_->gfxSelected, colors_.selected, thick11Px, matrix);
     rendererDataLock_.unlock();
 }
 
@@ -430,125 +206,151 @@ void FPGAViewWidget::renderLines(void)
     if (ctx_ == nullptr)
         return;
 
-    ctx_->lock_ui();
-
-    // For now, collapse any decal changes into change of all decals.
-    // TODO(q3k): fix this
-    bool decalsChanged = false;
-    if (ctx_->allUiReload) {
-        ctx_->allUiReload = false;
-        decalsChanged = true;
-    }
-    if (ctx_->frameUiReload) {
-        ctx_->frameUiReload = false;
-        decalsChanged = true;
-    }
-    if (ctx_->belUiReload.size() > 0) {
-        ctx_->belUiReload.clear();
-        decalsChanged = true;
-    }
-    if (ctx_->wireUiReload.size() > 0) {
-        ctx_->wireUiReload.clear();
-        decalsChanged = true;
-    }
-    if (ctx_->pipUiReload.size() > 0) {
-        ctx_->pipUiReload.clear();
-        decalsChanged = true;
-    }
-    if (ctx_->groupUiReload.size() > 0) {
-        ctx_->groupUiReload.clear();
-        decalsChanged = true;
-    }
-
-    // Local copy of decals, taken as fast as possible to not block the P&R.
-    std::vector<std::pair<BelId, DecalXY>> belDecals;
+    // Data from Context needed to render all decals.
+    std::vector<DecalXY> belDecals;
     std::vector<DecalXY> wireDecals;
     std::vector<DecalXY> pipDecals;
     std::vector<DecalXY> groupDecals;
-
-    if (decalsChanged) {
-        for (auto bel : ctx_->getBels()) {
-            belDecals.push_back(std::pair<BelId, DecalXY>(bel, ctx_->getBelDecal(bel)));
+    bool decalsChanged = false;
+    {
+        // Take the UI/Normal mutex on the Context, copy over all we need as
+        // fast as we can.
+        std::lock_guard<std::mutex> lock_ui(ctx_->ui_mutex);
+        std::lock_guard<std::mutex> lock(ctx_->mutex);
+
+        // For now, collapse any decal changes into change of all decals.
+        // TODO(q3k): fix this
+        if (ctx_->allUiReload) {
+            ctx_->allUiReload = false;
+            decalsChanged = true;
         }
-        for (auto wire : ctx_->getWires()) {
-            wireDecals.push_back(ctx_->getWireDecal(wire));
+        if (ctx_->frameUiReload) {
+            ctx_->frameUiReload = false;
+            decalsChanged = true;
         }
-        for (auto pip : ctx_->getPips()) {
-            pipDecals.push_back(ctx_->getPipDecal(pip));
+        if (ctx_->belUiReload.size() > 0) {
+            ctx_->belUiReload.clear();
+            decalsChanged = true;
         }
-        for (auto group : ctx_->getGroups()) {
-            groupDecals.push_back(ctx_->getGroupDecal(group));
+        if (ctx_->wireUiReload.size() > 0) {
+            ctx_->wireUiReload.clear();
+            decalsChanged = true;
+        }
+        if (ctx_->pipUiReload.size() > 0) {
+            ctx_->pipUiReload.clear();
+            decalsChanged = true;
+        }
+        if (ctx_->groupUiReload.size() > 0) {
+            ctx_->groupUiReload.clear();
+            decalsChanged = true;
+        }
+
+        // Local copy of decals, taken as fast as possible to not block the P&R.
+        if (decalsChanged) {
+            for (auto bel : ctx_->getBels()) {
+                belDecals.push_back(ctx_->getBelDecal(bel));
+            }
+            for (auto wire : ctx_->getWires()) {
+                wireDecals.push_back(ctx_->getWireDecal(wire));
+            }
+            for (auto pip : ctx_->getPips()) {
+                pipDecals.push_back(ctx_->getPipDecal(pip));
+            }
+            for (auto group : ctx_->getGroups()) {
+                groupDecals.push_back(ctx_->getGroupDecal(group));
+            }
         }
     }
-    ctx_->unlock_ui();
 
-    rendererArgsLock_.lock();
-    auto selectedItems = rendererArgs_->selectedItems;
-    auto highlightedItems = rendererArgs_->highlightedItems;
-    auto highlightedOrSelectedChanged = rendererArgs_->highlightedOrSelectedChanged;
-    rendererArgs_->highlightedOrSelectedChanged = false;
-    rendererArgsLock_.unlock();
+    // Arguments from the main UI thread on what we should render.
+    std::vector<DecalXY> selectedDecals;
+    std::vector<DecalXY> highlightedDecals[8];
+    bool highlightedOrSelectedChanged;
+    {
+        // Take the renderer arguments lock, copy over all we need.
+        QMutexLocker lock(&rendererArgsLock_);
+        selectedDecals = rendererArgs_->selectedDecals;
+        for (int i = 0; i < 8; i++)
+            highlightedDecals[i] = rendererArgs_->highlightedDecals[i];
+        highlightedOrSelectedChanged = rendererArgs_->highlightedOrSelectedChanged;
+        rendererArgs_->highlightedOrSelectedChanged = false;
+    }
 
     QuadTreeBels::BoundingBox globalBB = QuadTreeBels::BoundingBox(-1000, -1000, 1000, 1000);
 
+    // Render decals if necessary.
     if (decalsChanged) {
         auto data = std::unique_ptr<FPGAViewWidget::RendererData>(new FPGAViewWidget::RendererData);
         // Draw Bels.
         data->qtBels = std::unique_ptr<QuadTreeBels>(new QuadTreeBels(globalBB));
         for (auto const &decal : belDecals) {
-            drawDecal(data->decals, decal.second);
-            commitToQuadtree(data->qtBels.get(), decal.second, decal.first);
+            drawArchDecal(data->gfxByStyle, decal);
         }
         // Draw Wires.
         for (auto const &decal : wireDecals) {
-            drawDecal(data->decals, decal);
+            drawArchDecal(data->gfxByStyle, decal);
         }
         // Draw Pips.
         for (auto const &decal : pipDecals) {
-            drawDecal(data->decals, decal);
+            drawArchDecal(data->gfxByStyle, decal);
         }
         // Draw Groups.
         for (auto const &decal : groupDecals) {
-            drawDecal(data->decals, decal);
+            drawArchDecal(data->gfxByStyle, decal);
         }
 
         // Swap over.
-        rendererDataLock_.lock();
-        rendererData_ = std::move(data);
-        rendererDataLock_.unlock();
+        {
+            QMutexLocker lock(&rendererDataLock_);
+
+            // If we're not re-rendering any highlights/selections, let's
+            // copy them over from teh current object.
+            if (!highlightedOrSelectedChanged) {
+                data->gfxSelected = rendererData_->gfxSelected;
+                for (int i = 0; i < 8; i++)
+                    data->gfxHighlighted[i] = rendererData_->gfxHighlighted[i];
+            }
+
+            rendererData_ = std::move(data);
+        }
     }
 
-    rendererDataLock_.lock();
-    if (decalsChanged || highlightedOrSelectedChanged) {
-        rendererData_->selected.clear();
-        for (auto &decal : selectedItems) {
-            drawDecal(rendererData_->selected, decal);
+    if (highlightedOrSelectedChanged) {
+        QMutexLocker locker(&rendererDataLock_);
+
+        // Render selected.
+        rendererData_->gfxSelected.clear();
+        for (auto &decal : selectedDecals) {
+            drawDecal(rendererData_->gfxSelected, decal);
         }
+
+        // Render highlighted.
         for (int i = 0; i < 8; i++) {
-            rendererData_->highlighted[i].clear();
-            for (auto &decal : highlightedItems[i]) {
-                drawDecal(rendererData_->highlighted[i], decal);
+            rendererData_->gfxHighlighted[i].clear();
+            for (auto &decal : highlightedDecals[i]) {
+                drawDecal(rendererData_->gfxHighlighted[i], decal);
             }
         }
     }
-    rendererDataLock_.unlock();
 }
 
 void FPGAViewWidget::onSelectedArchItem(std::vector<DecalXY> decals)
 {
-    rendererArgsLock_.lock();
-    rendererArgs_->selectedItems = decals;
-    rendererArgs_->highlightedOrSelectedChanged = true;
-    rendererArgsLock_.unlock();
+    {
+        QMutexLocker locker(&rendererArgsLock_);
+        rendererArgs_->selectedDecals = decals;
+        rendererArgs_->highlightedOrSelectedChanged = true;
+    }
     pokeRenderer();
 }
 
 void FPGAViewWidget::onHighlightGroupChanged(std::vector<DecalXY> decals, int group)
 {
-    rendererArgsLock_.lock();
-    rendererArgs_->highlightedItems[group] = decals;
-    rendererArgs_->highlightedOrSelectedChanged = true;
-    rendererArgsLock_.unlock();
+    {
+        QMutexLocker locker(&rendererArgsLock_);
+        rendererArgs_->highlightedDecals[group] = decals;
+        rendererArgs_->highlightedOrSelectedChanged = true;
+    }
     pokeRenderer();
 }
 
@@ -557,7 +359,7 @@ void FPGAViewWidget::resizeGL(int width, int height) {}
 void FPGAViewWidget::mousePressEvent(QMouseEvent *event)
 {
     if (event->buttons() & Qt::RightButton || event->buttons() & Qt::MidButton) {
-        lastPos_ = event->pos();
+        lastDragPos_ = event->pos();
     }
     if (event->buttons() & Qt::LeftButton) {
         int x = event->x();
@@ -609,9 +411,9 @@ QVector4D FPGAViewWidget::mouseToWorldDimensions(int x, int y)
 void FPGAViewWidget::mouseMoveEvent(QMouseEvent *event)
 {
     if (event->buttons() & Qt::RightButton || event->buttons() & Qt::MidButton) {
-        const int dx = event->x() - lastPos_.x();
-        const int dy = event->y() - lastPos_.y();
-        lastPos_ = event->pos();
+        const int dx = event->x() - lastDragPos_.x();
+        const int dy = event->y() - lastDragPos_.y();
+        lastDragPos_ = event->pos();
 
         auto world = mouseToWorldDimensions(dx, dy);
         viewMove_.translate(world.x(), -world.y());