D3：在平移和縮放時保持SVG的相對位置

Question

我正在嘗試進行SVG平面圖的概念驗證，該平面圖可以平移和縮放，並且還可以在頂部放置標記。 縮放/平移發生時，標記不會停留在位置上。 我知道為什么會發生這種情況，但不確定在平移/縮放時將標記保持在適當位置的最佳方法。

這是代碼：

    var svg = d3.select(".floorplan")
  .attr("width", "100%")
  .attr("height", "100%")
  .call(d3.zoom().on("zoom", zoomed))
  .select("g")

  var marker = d3.selectAll(".marker")
    .call(d3.drag()
      .on("start", dragstarted)
      .on("drag", dragged)
      .on("end", dragended)
    )


  function zoomed() {
    svg.attr("transform", d3.event.transform);
  }

  function dragstarted(d) {
    console.log('dragstarted');
  }

  function dragged(d) {
    var x = d3.event.x;
    var y = d3.event.y;

    d3.select(this).attr("transform", "translate(" + x + "," + y + ")");
  }

  function dragended(d) {
    console.log('drag ended: marker:'+ d3.select(this).attr('data-id') + ' position: ' + d3.event.x +', ' + d3.event.y);
  }

還有一個Codepen可以在這里直觀地看到： https ://codepen.io/danielhoff/pen/WzQbRr

我還有其他限制，即標記元素不應包含在平面圖svg中。

Answer 1

這是您的Codepen的修改版本，可修正拖動事件期間標記的移動， 同時將標記保持在平面圖svg容器之外 ：

https://codepen.io/xavierguihot/pen/OvyRPY?editors=0010

---

回到上下文，一個簡單的解決方案是將標記元素包含在平面圖容器中（以使標記獲得與平面圖相同的縮放事件），但是在這里，我們希望標記位於其自己的svg中容器。

而且這不是小事！

---

Appart通過在html標記中包含ID（以便從html中選擇這些元素），僅對javascript部分進行了修改。

讓我們深入了解達到這一點所需的步驟：

首先：讓我們修改zoomed功能，使其同樣適用於標記：

最初，這是縮放功能：

function zoomed() {
  svg.attr("transform", d3.event.transform);
}

以及修改后的版本：

function zoomed() {

  // Before zooming the floor, let's find the previous scale of the floor:
  var curFloor = document.getElementById('floorplan');
  var curFloorScale = 1;
  if (curFloor.getAttribute("transform")) {
    var curFloorTransf = getTransformation(curFloor.getAttribute("transform"));
    curFloorScale = curFloorTransf.scaleX;
  }

  // Let's apply the zoom
  svg.attr("transform", d3.event.transform);

  // And let's now find the new scale of the floor:
  var newFloorTransf = getTransformation(curFloor.getAttribute("transform"));
  var newFloorScale = newFloorTransf.scaleX;

  // This way we get the diff of scale applied to the floor, which we'll apply to the marker:
  var dscale = newFloorScale - curFloorScale;

  // Then let's find the current x, y coordinates of the marker:
  var marker = document.getElementById('Layer_1');
  var currentTransf = getTransformation(marker.getAttribute("transform"));
  var currentx = currentTransf.translateX;
  var currenty = currentTransf.translateY;

  // And the position of the mouse:
  var center = d3.mouse(marker);

  // In order to find out the distance between the mouse and the marker:
  // (43 is based on the size of the marker)
  var dx = currentx - center[0] + 43;
  var dy = currenty - center[1];

  // Which allows us to find out the exact place of the new x, y coordinates of the marker after the zoom:
  // 38.5 and 39.8 comes from the ratio between the size of the floor container and the marker container.
  // "/2" comes (I think) from the fact that the floor container is initially translated at the center of the screen:
  var newx = currentx + dx * dscale / (38.5/2);
  var newy = currenty + dy * dscale / (39.8/2);

  // And we can finally apply the translation/scale of the marker!:
  d3.selectAll(".marker").attr("transform", "translate(" + newx + "," + newy + ") scale(" + d3.event.transform.k + ")");
}

這大量使用getTransformation函數，該函數允許檢索元素的當前轉換詳細信息。

然后：但是現在，在縮放后，當我們拖動標記時，它會恢復其原始大小：

這意味着在應用拖動變換時，我們必須調整標記的拖動功能以保持其當前縮放比例：

這是最初的拖動功能：

function dragged(d) {
  var x = d3.event.x;
  var y = d3.event.y;
  d3.select(this).attr("transform", "translate(" + x + "," + y + ")");
}

及其修改版本：

function draggedMarker(d) {

  var x = d3.event.x;
  var y = d3.event.y;

  // As we want to keep the same current scale of the marker during the transform, let's find out the current scale of the marker:
  var marker = document.getElementById('Layer_1');
  var curScale = 1;
  if (marker.getAttribute("transform")) {
    curScale = getTransformation(marker.getAttribute("transform")).scaleX;
  }

  // We can thus apply the translate And keep the current scale:
  d3.select(this).attr("transform", "translate(" + x + "," + y + "), scale(" + curScale + ")");
}

最后：拖動地板時，我們還必須相應地拖動標記：

因此，我們必須覆蓋地板的默認拖動，以便將相同的dragg事件包括到標記中。

這是應用於地板的拖動功能：

function draggedFloor(d) {

  // Overriding the floor drag to do the exact same thing as the default drag behaviour^^:

  var dx = d3.event.dx;
  var dy = d3.event.dy;

  var curFloor = document.getElementById('svg-floor');
  var curScale = 1;
  var curx = 0;
  var cury = 0;
  if (curFloor.getAttribute("transform")) {
    curScale = getTransformation(curFloor.getAttribute("transform")).scaleX;
    curx = getTransformation(curFloor.getAttribute("transform")).translateX;
    cury = getTransformation(curFloor.getAttribute("transform")).translateY;
  }

  d3.select(this).attr("transform", "translate(" + (curx + dx) + "," + (cury + dy) + ")");

  // We had to override the floor drag in order to include in the same method the drag of the marker:

  var marker = document.getElementById('Layer_1');
  var currentTransf = getTransformation(marker.getAttribute("transform"));

  var currentx = currentTransf.translateX;
  var currenty = currentTransf.translateY;
  var currentScale = currentTransf.scaleX;

  d3.selectAll(".marker").attr("transform", "translate(" + (currentx + dx) + "," + (currenty + dy) + ") scale(" + currentScale + ")");
}