diff data/model/RelativelyFineZoomConstraint.cpp @ 1552:05c3fbaec8ea

Introduce RelativelyFineZoomConstraint, which encodes more-or-less the scheme that was already used for the horizontal thumbwheel in the pane (which overrode the layers' own zoom constraints unless they said they couldn't support any other)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/model/RelativelyFineZoomConstraint.cpp	Wed Oct 10 14:32:34 2018 +0100
@@ -0,0 +1,101 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Sonic Visualiser
+    An audio file viewer and annotation editor.
+    Centre for Digital Music, Queen Mary, University of London.
+    
+    This program is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#include "RelativelyFineZoomConstraint.h"
+
+#include <vector>
+#include <algorithm>
+#include <iostream>
+
+using namespace std;
+
+ZoomLevel
+RelativelyFineZoomConstraint::getNearestZoomLevel(ZoomLevel requested,
+                                                  RoundingDirection dir) const
+{
+    static vector<int> levels;
+
+    int maxLevel = getMaxZoomLevel().level;
+
+    if (levels.empty()) {
+        int level = 1;
+        while (level <= maxLevel) {
+//            cerr << level << " ";
+            levels.push_back(level);
+            int step = level / 10;
+            int pwr = 0;
+            while (step > 0) {
+                ++pwr;
+                step /= 2;
+            }
+            step = (1 << pwr);
+            level += step;
+        }
+//        cerr << endl;
+    }
+
+    RoundingDirection effective = dir;
+    if (requested.zone == ZoomLevel::PixelsPerFrame) {
+        if (dir == RoundUp) effective = RoundDown;
+        else if (dir == RoundDown) effective = RoundUp;
+    }
+
+    // iterator pointing to first level that is >= requested
+    auto i = lower_bound(levels.begin(), levels.end(), requested.level);
+
+    ZoomLevel newLevel(requested);
+
+    if (i == levels.end()) {
+        newLevel.level = maxLevel;
+
+    } else if (*i == requested.level) {
+        newLevel.level = requested.level;
+
+    } else if (effective == RoundUp) {
+        newLevel.level = *i;
+
+    } else if (effective == RoundDown) {
+        if (i != levels.begin()) {
+            --i;
+        }
+        newLevel.level = *i;
+
+    } else { // RoundNearest
+        if (i != levels.begin()) {
+            auto j = i;
+            --j;
+            if (requested.level - *j < *i - requested.level) {
+                newLevel.level = *j;
+            } else {
+                newLevel.level = *i;
+            }
+        }
+    }
+
+    // canonicalise
+    if (newLevel.level == 1) {
+        newLevel.zone = ZoomLevel::FramesPerPixel;
+    }
+
+    using namespace std::rel_ops;
+    if (newLevel > getMaxZoomLevel()) {
+        newLevel = getMaxZoomLevel();
+    } else if (newLevel < getMinZoomLevel()) {
+        newLevel = getMinZoomLevel();
+    }
+    
+    return newLevel;
+}
+
+