fix(iv): do not resize on open and other zoom fixes (#4766)

Fixes #4718

See the demo of problems that were fixed and of fixes in action over
here: https://www.loom.com/share/3bdee20b32434e0bbba47d393928d4f7

There are fixed for three problems:
1) Window is not resizing when new image is loaded in (it still does
when image being loaded is the only one)
2) When you using scroll mouse wheel it is taking into account where the
cursor is (there is some corner case when it doesn't do it perfectly,
that I can't catch when it doesn't follow it exactly, but a bit of
panning fixes it)
~~3) Switching between images recenters (if image is smaller) or making
some other panning nessery to have image in the viewport. I believe it
is doing same stuff what happens when window is resized.~~ This has been
reverted.

---------

Signed-off-by: Aleksandr Motsjonov <soswow@gmail.com>

Author: soswow

.gitignore

@@ -23,6 +23,7 @@ gastest.o
 /*.exr
 /*.tif
 /*.jpg
+/*.png
 /*.jxl
 /*.tx
 /*.log

src/iv/imageviewer.cpp

@@ -854,14 +854,11 @@ ImageViewer::open()
         if (filename.empty())
             continue;
         add_image(filename);
-        //        int n = m_images.size()-1;
-        //        IvImage *newimage = m_images[n];
-        //        newimage->read_iv (0, false, image_progress_callback, this);
     }
+
     if (old_lastimage >= 0) {
         // Otherwise, add_image already did this for us.
         current_image(old_lastimage + 1);
-        fitWindowToImage(true, true);
     }
 }
 
@@ -887,7 +884,6 @@ ImageViewer::openRecentFile()
         if (m_images.size() > 1) {
             // Otherwise, add_image already did this for us.
             current_image(m_images.size() - 1);
-            fitWindowToImage(true, true);
         }
     }
 }
@@ -2009,67 +2005,59 @@ ImageViewer::print()
 }
 
 
-
 void
-ImageViewer::zoomIn()
+ImageViewer::zoomIn(bool smooth)
 {
     IvImage* img = cur();
     if (!img)
         return;
-    if (zoom() >= 64)
+
+    float current_zoom = zoom();
+    if (current_zoom >= 64)
         return;
-    float oldzoom = zoom();
-    float newzoom = ceil2f(oldzoom);
 
-    float xc, yc;  // Center view position
-    glwin->get_center(xc, yc);
-    int xm, ym;  // Mouse position
-    glwin->get_focus_image_pixel(xm, ym);
-    float xoffset      = xc - xm;
-    float yoffset      = yc - ym;
-    float maxzoomratio = std::max(oldzoom / newzoom, newzoom / oldzoom);
-    int nsteps         = (int)OIIO::clamp(20 * (maxzoomratio - 1), 2.0f, 10.0f);
-    for (int i = 1; i <= nsteps; ++i) {
-        float a         = (float)i / (float)nsteps;  // Interpolation amount
-        float z         = OIIO::lerp(oldzoom, newzoom, a);
-        float zoomratio = z / oldzoom;
-        view(xm + xoffset / zoomratio, ym + yoffset / zoomratio, z, false);
-        if (i != nsteps) {
-            QApplication::processEvents();
-            Sysutil::usleep(1000000 / 4 / nsteps);
-        }
-    }
+    float newzoom = ceil2f(current_zoom);
 
-    fitImageToWindowAct->setChecked(false);
+    this->zoomToCursor(newzoom, smooth);
 }
 
 
-
 void
-ImageViewer::zoomOut()
+ImageViewer::zoomOut(bool smooth)
 {
     IvImage* img = cur();
     if (!img)
         return;
-    if (zoom() <= 1.0f / 64)
+
+    float current_zoom = zoom();
+    if (current_zoom <= 1.0f / 64)
         return;
+
+    float newzoom = floor2f(current_zoom);
+
+    this->zoomToCursor(newzoom, smooth);
+}
+
+
+void
+ImageViewer::zoomToCursor(float newzoom, bool smooth)
+{
     float oldzoom = zoom();
-    float newzoom = floor2f(oldzoom);
-
-    float xcpel, ycpel;  // Center view position
-    glwin->get_center(xcpel, ycpel);
-    int xmpel, ympel;  // Mouse position
-    glwin->get_focus_image_pixel(xmpel, ympel);
-    float xoffset      = xcpel - xmpel;
-    float yoffset      = ycpel - ympel;
+    float xc, yc;  // Center view position
+    glwin->get_center(xc, yc);
+    int xm, ym;  // Mouse position
+    glwin->get_focus_image_pixel(xm, ym);
+    float xoffset = xc - xm;
+    float yoffset = yc - ym;
+
     float maxzoomratio = std::max(oldzoom / newzoom, newzoom / oldzoom);
-    int nsteps         = (int)OIIO::clamp(20 * (maxzoomratio - 1), 2.0f, 10.0f);
+    int nsteps = smooth ? (int)OIIO::clamp(20 * (maxzoomratio - 1), 2.0f, 10.0f)
+                        : 1;
     for (int i = 1; i <= nsteps; ++i) {
         float a         = (float)i / (float)nsteps;  // Interpolation amount
         float z         = OIIO::lerp(oldzoom, newzoom, a);
         float zoomratio = z / oldzoom;
-        view(xmpel + xoffset / zoomratio, ympel + yoffset / zoomratio, z,
-             false);
+        view(xm + xoffset / zoomratio, ym + yoffset / zoomratio, z, false);
         if (i != nsteps) {
             QApplication::processEvents();
             Sysutil::usleep(1000000 / 4 / nsteps);

src/iv/imageviewer.h

@@ -265,10 +265,12 @@ private slots:
     void moveToNewWindow();     ///< Split current image off as a new window
     void print();               ///< Print current image
     void deleteCurrentImage();  ///< Deleting displayed image
-    void zoomIn();              ///< Zoom in to next power of 2
-    void zoomOut();             ///< Zoom out to next power of 2
-    void normalSize();          ///< Adjust zoom to 1:1
-    void fitImageToWindow();    ///< Adjust zoom to fit window exactly
+    void zoomIn(bool smooth = true);   ///< Zoom in to next power of 2
+    void zoomOut(bool smooth = true);  ///< Zoom out to next power of 2
+    void zoomToCursor(float newzoom,
+                      bool smooth = true);  ///< Zoom to a specific level
+    void normalSize();                      ///< Adjust zoom to 1:1
+    void fitImageToWindow();  ///< Adjust zoom to fit window exactly
     /// Resize window to fit image exactly.  If zoomok is false, do not
     /// change the zoom, even to fit on screen. If minsize is true, do not
     /// resize smaller than default_width x default_height.

src/iv/ivgl.cpp

@@ -1218,13 +1218,13 @@ IvGL::mousePressEvent(QMouseEvent* event)
         switch (event->button()) {
         case Qt::LeftButton:
             if (mousemode == ImageViewer::MouseModeZoom && !Alt)
-                m_viewer.zoomIn();
+                m_viewer.zoomIn(true);  // Animated zoom for mouse clicks
             else
                 m_dragging = true;
             return;
         case Qt::RightButton:
             if (mousemode == ImageViewer::MouseModeZoom && !Alt)
-                m_viewer.zoomOut();
+                m_viewer.zoomOut(true);  // Animated zoom for mouse clicks
             else
                 m_dragging = true;
             return;
@@ -1328,9 +1328,11 @@ IvGL::wheelEvent(QWheelEvent* event)
     QPoint angdelta    = event->angleDelta() / 8;  // div by 8 to get degrees
     if (abs(angdelta.y()) > abs(angdelta.x())      // predominantly vertical
         && abs(angdelta.y()) > 2) {                // suppress tiny motions
-        float oldzoom = m_viewer.zoom();
-        float newzoom = (angdelta.y() > 0) ? ceil2f(oldzoom) : floor2f(oldzoom);
-        m_viewer.zoom(newzoom);
+        if (angdelta.y() > 0) {
+            m_viewer.zoomIn(false);
+        } else {
+            m_viewer.zoomOut(false);
+        }
         event->accept();
     }
     // TODO: Update this to keep the zoom centered on the event .x, .y

src/libtexture/imagecache_pvt.h

@@ -266,7 +266,7 @@ class OIIO_API ImageCacheFile final : public RefCnt {
     /// precompute.
     struct LevelInfo {
         std::unique_ptr<ImageSpec> m_spec;  ///< ImageSpec for the mip level,
-            // only specified if different from nativespec
+        // only specified if different from nativespec
         ImageSpec nativespec;  ///< Native ImageSpec for the mip level
         mutable std::unique_ptr<float[]> polecolor;  ///< Pole colors
         atomic_ll* tiles_read;  ///< Bitfield for tiles read at least once
@@ -394,10 +394,10 @@ class OIIO_API ImageCacheFile final : public RefCnt {
     std::atomic<std::shared_ptr<ImageInput>> m_input;
 #else
     std::shared_ptr<ImageInput> m_input;  ///< Open ImageInput, NULL if closed
-        // Note that m_input, the shared pointer itself, is NOT safe to
-        // access directly. ALWAYS retrieve its value with get_imageinput
-        // (it's thread-safe to use that result) and set its value with
-        // set_imageinput -- those are guaranteed thread-safe.
+    // Note that m_input, the shared pointer itself, is NOT safe to
+    // access directly. ALWAYS retrieve its value with get_imageinput
+    // (it's thread-safe to use that result) and set its value with
+    // set_imageinput -- those are guaranteed thread-safe.
 #endif
     std::vector<SubimageInfo> m_subimages;  ///< Info on each subimage
     TexFormat m_texformat;                  ///< Which texture format