Added convenient and efficient Timer class

The Timer is efficient because it does not depend on incrementing a
counter to keep track of time, nor does it call SDL_GetTicks every time
its state is checked (this happens once per frame instead).

Along with global functions Time::absoluteTimeMs() and
Time::deltaTimeMs(), this replaces previous globals tick_time, cur_time
and get_elapsed_time().

For now, there is still a fixed 100 times per second logic call rate,
but the new Time::deltaTimeMs() function should allow getting rid of
this.

11 files changed, 145 insertions, 154 deletions

diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index 26d0913e..2ff697c7 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -158,7 +158,7 @@ Gui::~Gui()
 void Gui::logic()
 {
     // Hide mouse cursor after extended inactivity
-    if (get_elapsed_time(mLastMouseActivityTime) > 15000)
+    if (mMouseActivityTimer.passed())
         SDL_ShowCursor(SDL_DISABLE);
 
     Palette::advanceGradients();
@@ -239,7 +239,7 @@ void Gui::updateCursor()
 void Gui::handleMouseMoved(const gcn::MouseInput &mouseInput)
 {
     gcn::Gui::handleMouseMoved(mouseInput);
-    mLastMouseActivityTime = tick_time;
+    mMouseActivityTimer.set(15000);
 
     // Make sure the cursor is visible
     SDL_ShowCursor(SDL_ENABLE);
diff --git a/src/gui/gui.h b/src/gui/gui.h
index 7c3c3afd..fd1dcf94 100644
--- a/src/gui/gui.h
+++ b/src/gui/gui.h
@@ -25,6 +25,8 @@
 #include "eventlistener.h"
 #include "guichanfwd.h"
 
+#include "utils/time.h"
+
 #include <guichan/gui.hpp>
 
 #include <SDL.h>
@@ -137,7 +139,7 @@ class Gui final : public gcn::Gui, public EventListener
         float mCustomCursorScale = 1.0f;
         std::vector<SDL_Cursor *> mSystemMouseCursors;
         std::vector<SDL_Cursor *> mCustomMouseCursors;
-        int mLastMouseActivityTime = 0;
+        Timer mMouseActivityTimer;
         Cursor mCursorType = Cursor::POINTER;
 };
 
diff --git a/src/gui/ministatuswindow.cpp b/src/gui/ministatuswindow.cpp
index d3e01bd2..e22172bc 100644
--- a/src/gui/ministatuswindow.cpp
+++ b/src/gui/ministatuswindow.cpp
@@ -43,8 +43,7 @@
 
 #include "utils/gettext.h"
 #include "utils/stringutils.h"
-
-extern volatile int tick_time;
+#include "utils/time.h"
 
 MiniStatusWindow::MiniStatusWindow():
     Popup("MiniStatus")
@@ -227,7 +226,7 @@ void MiniStatusWindow::logic()
 
     for (auto &icon : mIcons)
         if (icon)
-            icon->update(tick_time * 10);
+            icon->update(Time::absoluteTimeMs());
 }
 
 void MiniStatusWindow::mouseMoved(gcn::MouseEvent &event)
diff --git a/src/gui/palette.cpp b/src/gui/palette.cpp
index aaa3165c..6c6e6f06 100644
--- a/src/gui/palette.cpp
+++ b/src/gui/palette.cpp
@@ -22,18 +22,11 @@
 
 #include "palette.h"
 
-#include "configuration.h"
-#include "client.h"
-
-#include "gui/gui.h"
-
-#include "utils/gettext.h"
-#include "utils/stringutils.h"
-
 #include <cmath>
 
-static const double PI = 3.14159265;
+static constexpr double PI = 3.14159265;
 const gcn::Color Palette::BLACK = gcn::Color(0, 0, 0);
+Timer Palette::mRainbowTimer;
 Palette::Palettes Palette::mInstances;
 
 const gcn::Color Palette::RAINBOW_COLORS[7] = {
@@ -49,7 +42,6 @@ const gcn::Color Palette::RAINBOW_COLORS[7] = {
 const int Palette::RAINBOW_COLOR_COUNT = 7;
 
 Palette::Palette(int size) :
-    mRainbowTime(tick_time),
     mColors(size)
 {
     mInstances.insert(this);
@@ -76,97 +68,85 @@ const gcn::Color &Palette::getColor(char c, bool &valid)
 
 void Palette::advanceGradients()
 {
-    auto it = mInstances.begin();
-    auto it_end = mInstances.end();
+    const int advance = mRainbowTimer.elapsed() / 5;
+    if (advance <= 0)
+        return;
 
-    for (; it != it_end; it++)
-    {
-        (*it)->advanceGradient();
-    }
+    mRainbowTimer.extend(advance * 5);
+
+    for (auto palette : mInstances)
+        palette->advanceGradient(advance);
 }
 
-void Palette::advanceGradient()
+void Palette::advanceGradient(int advance)
 {
-    if (get_elapsed_time(mRainbowTime) > 5)
+    for (auto elem : mGradVector)
     {
-        int pos, colIndex, colVal, delay, numOfColors;
-        // For slower systems, advance can be greater than one (advance > 1
-        // skips advance-1 steps). Should make gradient look the same
-        // independent of the framerate.
-        int advance = get_elapsed_time(mRainbowTime) / 5;
-        double startColVal, destColVal;
-
-        for (auto &elem : mGradVector)
-        {
-            delay = elem->delay;
+        int delay = elem->delay;
 
-            if (elem->grad == PULSE)
-                delay = delay / 20;
+        if (elem->grad == PULSE)
+            delay = delay / 20;
 
-            numOfColors = (elem->grad == SPECTRUM ? 6 :
-                           elem->grad == PULSE ? 127 :
-                           RAINBOW_COLOR_COUNT);
+        const int numOfColors = (elem->grad == SPECTRUM ? 6 :
+                                 elem->grad == PULSE ? 127 :
+                                 RAINBOW_COLOR_COUNT);
 
-            elem->gradientIndex =
-                                    (elem->gradientIndex + advance) %
-                                    (delay * numOfColors);
+        elem->gradientIndex = (elem->gradientIndex + advance) %
+                              (delay * numOfColors);
 
-            pos = elem->gradientIndex % delay;
-            colIndex = elem->gradientIndex / delay;
+        const int pos = elem->gradientIndex % delay;
+        const int colIndex = elem->gradientIndex / delay;
 
-            if (elem->grad == PULSE)
-            {
-                colVal = (int) (255.0 * sin(PI * colIndex / numOfColors));
+        if (elem->grad == PULSE)
+        {
+            const int colVal = (int) (255.0 * sin(PI * colIndex / numOfColors));
+            const gcn::Color &col = elem->testColor;
 
-                const gcn::Color &col = elem->testColor;
+            elem->color.r = ((colVal * col.r) / 255) % (col.r + 1);
+            elem->color.g = ((colVal * col.g) / 255) % (col.g + 1);
+            elem->color.b = ((colVal * col.b) / 255) % (col.b + 1);
+        }
+        if (elem->grad == SPECTRUM)
+        {
+            int colVal;
 
-                elem->color.r = ((colVal * col.r) / 255) % (col.r + 1);
-                elem->color.g = ((colVal * col.g) / 255) % (col.g + 1);
-                elem->color.b = ((colVal * col.b) / 255) % (col.b + 1);
+            if (colIndex % 2)
+            { // falling curve
+                colVal = (int)(255.0 * (cos(PI * pos / delay) + 1) / 2);
             }
-            if (elem->grad == SPECTRUM)
-            {
-                if (colIndex % 2)
-                { // falling curve
-                    colVal = (int)(255.0 * (cos(PI * pos / delay) + 1) / 2);
-                }
-                else
-                { // ascending curve
-                    colVal = (int)(255.0 * (cos(PI * (delay - pos) / delay) +
-                                   1) / 2);
-                }
-
-                elem->color.r =
-                        (colIndex == 0 || colIndex == 5) ? 255 :
-                        (colIndex == 1 || colIndex == 4) ? colVal : 0;
-                elem->color.g =
-                        (colIndex == 1 || colIndex == 2) ? 255 :
-                        (colIndex == 0 || colIndex == 3) ? colVal : 0;
-                elem->color.b =
-                        (colIndex == 3 || colIndex == 4) ? 255 :
-                        (colIndex == 2 || colIndex == 5) ? colVal : 0;
+            else
+            { // ascending curve
+                colVal = (int)(255.0 * (cos(PI * (delay - pos) / delay) +
+                                1) / 2);
             }
-            else if (elem->grad == RAINBOW)
-            {
-                const gcn::Color &startCol = RAINBOW_COLORS[colIndex];
-                const gcn::Color &destCol =
-                        RAINBOW_COLORS[(colIndex + 1) % numOfColors];
 
-                startColVal = (cos(PI * pos / delay) + 1) / 2;
-                destColVal = 1 - startColVal;
+            elem->color.r =
+                    (colIndex == 0 || colIndex == 5) ? 255 :
+                    (colIndex == 1 || colIndex == 4) ? colVal : 0;
+            elem->color.g =
+                    (colIndex == 1 || colIndex == 2) ? 255 :
+                    (colIndex == 0 || colIndex == 3) ? colVal : 0;
+            elem->color.b =
+                    (colIndex == 3 || colIndex == 4) ? 255 :
+                    (colIndex == 2 || colIndex == 5) ? colVal : 0;
+        }
+        else if (elem->grad == RAINBOW)
+        {
+            const gcn::Color &startCol = RAINBOW_COLORS[colIndex];
+            const gcn::Color &destCol =
+                    RAINBOW_COLORS[(colIndex + 1) % numOfColors];
 
-                elem->color.r =(int)(startColVal * startCol.r +
-                                               destColVal * destCol.r);
+            const double startColVal = (cos(PI * pos / delay) + 1) / 2;
+            const double destColVal = 1 - startColVal;
 
-                elem->color.g =(int)(startColVal * startCol.g +
-                                               destColVal * destCol.g);
+            elem->color.r =(int)(startColVal * startCol.r +
+                                            destColVal * destCol.r);
 
-                elem->color.b =(int)(startColVal * startCol.b +
-                                               destColVal * destCol.b);
-            }
-        }
+            elem->color.g =(int)(startColVal * startCol.g +
+                                            destColVal * destCol.g);
 
-        if (advance)
-            mRainbowTime = tick_time;
+            elem->color.b =(int)(startColVal * startCol.b +
+                                            destColVal * destCol.b);
+        }
     }
 }
diff --git a/src/gui/palette.h b/src/gui/palette.h
index 41378a43..b81d8865 100644
--- a/src/gui/palette.h
+++ b/src/gui/palette.h
@@ -23,6 +23,8 @@
 #ifndef PALETTE_H
 #define PALETTE_H
 
+#include "utils/time.h"
+
 #include <guichan/color.hpp>
 
 #include <cstdlib>
@@ -121,8 +123,8 @@ class Palette
         static const gcn::Color RAINBOW_COLORS[];
         static const int RAINBOW_COLOR_COUNT;
 
-        /** Time tick, that gradient-type colors were updated the last time. */
-        int mRainbowTime;
+        /** Timer used when updating gradient-type colors. */
+        static Timer mRainbowTimer;
 
         using Palettes = std::set<Palette *>;
         static Palettes mInstances;
@@ -131,7 +133,7 @@ class Palette
 
         ~Palette();
 
-        void advanceGradient();
+        void advanceGradient(int advance);
 
         struct ColorElem
         {
@@ -147,7 +149,7 @@ class Palette
             int delay;
             int committedDelay;
 
-            void set(int type, gcn::Color &color, GradientType grad, int delay)
+            void set(int type, const gcn::Color &color, GradientType grad, int delay)
             {
                 ColorElem::type = type;
                 ColorElem::color = color;
diff --git a/src/gui/socialwindow.cpp b/src/gui/socialwindow.cpp
index 76235306..79a0fd53 100644
--- a/src/gui/socialwindow.cpp
+++ b/src/gui/socialwindow.cpp
@@ -262,7 +262,7 @@ private:
 class PlayerListTab : public SocialTab
 {
 public:
-    PlayerListTab() 
+    PlayerListTab()
     {
         mPlayerList = new PlayerList;
 
@@ -679,10 +679,10 @@ void SocialWindow::setPlayersOnline(const std::vector<Avatar*> &players)
 
 void SocialWindow::logic()
 {
-    if (mLastOnlineListUpdate == 0 || get_elapsed_time(mLastOnlineListUpdate) >= 18000)
+    if (mOnlineListUpdateTimer.passed())
     {
         Net::getChatHandler()->requestOnlineList();
-        mLastOnlineListUpdate = tick_time;
+        mOnlineListUpdateTimer.set(18000);
     }
 
     Window::logic();
diff --git a/src/gui/socialwindow.h b/src/gui/socialwindow.h
index b6865fb2..350f919c 100644
--- a/src/gui/socialwindow.h
+++ b/src/gui/socialwindow.h
@@ -21,6 +21,8 @@
 #ifndef SOCIALWINDOW_H
 #define SOCIALWINDOW_H
 
+#include "utils/time.h"
+
 #include "gui/widgets/window.h"
 
 #include <guichan/actionevent.hpp>
@@ -87,7 +89,7 @@ protected:
     void updateButtons();
 
     int mGuildInvited = 0;
-    int mLastOnlineListUpdate = 0;
+    Timer mOnlineListUpdateTimer;
     ConfirmDialog *mGuildAcceptDialog = nullptr;
     TextDialog *mGuildCreateDialog = nullptr;
 
diff --git a/src/gui/viewport.cpp b/src/gui/viewport.cpp
index cdc4076e..8dbdf7c7 100644
--- a/src/gui/viewport.cpp
+++ b/src/gui/viewport.cpp
@@ -79,8 +79,6 @@ void Viewport::setMap(Map *map)
 
 void Viewport::draw(gcn::Graphics *gcnGraphics)
 {
-    static int lastTick = tick_time;
-
     // Check whether map was successfully loaded since
     // the rest of this function relies on it
     if (!mMap || !local_player)
@@ -95,12 +93,6 @@ void Viewport::draw(gcn::Graphics *gcnGraphics)
 
     auto *graphics = static_cast<Graphics*>(gcnGraphics);
 
-    // Avoid freaking out when tick_time overflows
-    if (tick_time < lastTick)
-    {
-        lastTick = tick_time;
-    }
-
     // Calculate viewpoint
     int midTileX = (graphics->getWidth() + mScrollCenterOffsetX) / 2;
     int midTileY = (graphics->getHeight() + mScrollCenterOffsetX) / 2;
@@ -109,49 +101,57 @@ void Viewport::draw(gcn::Graphics *gcnGraphics)
     const int player_x = (int) playerPos.x - midTileX;
     const int player_y = (int) playerPos.y - midTileY;
 
-    if (mScrollLaziness < 1)
-        mScrollLaziness = 1; // Avoids division by zero
+    const float ticks = Time::deltaTimeMs() / static_cast<float>(MILLISECONDS_IN_A_TICK);
+    float scrollFraction = 1.0f;
 
-    while (lastTick < tick_time)
+    if (mScrollLaziness > 1)
     {
-        // Apply lazy scrolling
-        if (player_x > mPixelViewX + mScrollRadius)
-        {
-            mPixelViewX += (player_x - mPixelViewX - mScrollRadius) /
-                            mScrollLaziness;
-        }
-        if (player_x < mPixelViewX - mScrollRadius)
-        {
-            mPixelViewX += (player_x - mPixelViewX + mScrollRadius) /
-                            mScrollLaziness;
-        }
-        if (player_y > mPixelViewY + mScrollRadius)
-        {
-            mPixelViewY += (player_y - mPixelViewY - mScrollRadius) /
-                            mScrollLaziness;
-        }
-        if (player_y < mPixelViewY - mScrollRadius)
-        {
-            mPixelViewY += (player_y - mPixelViewY + mScrollRadius) /
-                            mScrollLaziness;
-        }
+        // mScrollLaziness defines the fraction of the desired camera movement
+        // that is applied every 10ms. To make this work independently of the
+        // frame duration, we calculate the actual scroll fraction based on the
+        // time delta.
+        scrollFraction = 1.0f - std::pow(1.0f - 1.0f / mScrollLaziness, ticks);
+    }
+
+    // Apply lazy scrolling
+    if (player_x > mPixelViewX + mScrollRadius)
+    {
+        mPixelViewX += (player_x - mPixelViewX - mScrollRadius) *
+                        scrollFraction;
+    }
+    if (player_x < mPixelViewX - mScrollRadius)
+    {
+        mPixelViewX += (player_x - mPixelViewX + mScrollRadius) *
+                        scrollFraction;
+    }
+    if (player_y > mPixelViewY + mScrollRadius)
+    {
+        mPixelViewY += (player_y - mPixelViewY - mScrollRadius) *
+                        scrollFraction;
+    }
+    if (player_y < mPixelViewY - mScrollRadius)
+    {
+        mPixelViewY += (player_y - mPixelViewY + mScrollRadius) *
+                        scrollFraction;
+    }
+
+    // manage shake effect
+    for (auto i = mShakeEffects.begin(); i != mShakeEffects.end(); i++)
+    {
+        // The decay defines the reduction in amplitude per 10ms. Here
+        // we calculate the reduction based on the ticks.
+        const float decay = std::pow(i->decay, ticks);
+
+        // apply the effect to viewport
+        mPixelViewX += i->x *= -decay;
+        mPixelViewY += i->y *= -decay;
 
-        // manage shake effect
-        for (auto i = mShakeEffects.begin();
-             i != mShakeEffects.end();
-             i++)
+        // check death conditions
+        if (std::abs(i->x) + std::abs(i->y) < 1.0f ||
+            (i->timer.isSet() && i->timer.passed()))
         {
-            // apply the effect to viewport
-            mPixelViewX += i->x *= -i->decay;
-            mPixelViewY += i->y *= -i->decay;
-            // check death conditions
-            if (abs(i->x) + abs(i->y) < 1.0f ||
-                (i->duration > 0 && --i->duration == 0))
-            {
-                i = mShakeEffects.erase(i);
-            }
+            i = mShakeEffects.erase(i);
         }
-        lastTick++;
     }
 
     // Auto center when player is off screen
@@ -264,7 +264,9 @@ void Viewport::shakeScreen(float x, float y, float decay, unsigned duration)
     effect.x = x;
     effect.y = y;
     effect.decay = decay;
-    effect.duration = duration;
+
+    if (duration > 0)
+        effect.timer.set(duration * MILLISECONDS_IN_A_TICK);
 }
 
 void Viewport::logic()
@@ -528,9 +530,9 @@ void Viewport::mouseDragged(gcn::MouseEvent &event)
 
     if (mPlayerFollowMouse && !event.isShiftPressed())
     {
-        if (get_elapsed_time(mLocalWalkTime) >= walkingMouseDelay)
+        if (mLocalWalkTimer.passed())
         {
-            mLocalWalkTime = tick_time;
+            mLocalWalkTimer.set(walkingMouseDelay);
             local_player->setDestination(event.getX() + (int) mPixelViewX,
                                          event.getY() + (int) mPixelViewY);
             local_player->pathSetByMouse();
diff --git a/src/gui/viewport.h b/src/gui/viewport.h
index 32d9bd5c..53edb50f 100644
--- a/src/gui/viewport.h
+++ b/src/gui/viewport.h
@@ -25,6 +25,8 @@
 #include "eventlistener.h"
 #include "position.h"
 
+#include "utils/time.h"
+
 #include "gui/widgets/windowcontainer.h"
 
 #include <guichan/mouselistener.hpp>
@@ -207,15 +209,15 @@ class Viewport : public WindowContainer, public gcn::MouseListener,
             float x;
             float y;
             float decay;
-            unsigned duration;
+            Timer timer;
         };
         std::list<ShakeEffect> mShakeEffects;
 
         bool mPlayerFollowMouse = false;
 
-        int mLocalWalkTime = -1; /**< Timestamp before the next walk can be sent. */
+        Timer mLocalWalkTimer;      /**< Timer for sending walk messages. */
 
-        PopupMenu *mPopupMenu;       /**< Popup menu. */
+        PopupMenu *mPopupMenu;              /**< Popup menu. */
         Being *mHoverBeing = nullptr;       /**< Being mouse is currently over. */
         FloorItem *mHoverItem = nullptr;    /**< FloorItem mouse is currently over. */
         BeingPopup *mBeingPopup;            /**< Being information popup. */
diff --git a/src/gui/widgets/browserbox.cpp b/src/gui/widgets/browserbox.cpp
index 40c9b66a..9eee9448 100644
--- a/src/gui/widgets/browserbox.cpp
+++ b/src/gui/widgets/browserbox.cpp
@@ -22,8 +22,6 @@
 
 #include "gui/widgets/browserbox.h"
 
-#include "client.h"
-
 #include "gui/gui.h"
 #include "gui/truetypefont.h"
 #include "gui/widgets/linkhandler.h"
@@ -32,6 +30,8 @@
 #include "resources/iteminfo.h"
 #include "resources/theme.h"
 
+#include "utils/stringutils.h"
+
 #include <guichan/graphics.hpp>
 #include <guichan/font.hpp>
 #include <guichan/cliprectangle.hpp>
@@ -276,7 +276,7 @@ void BrowserBox::relayoutText()
         layoutTextRow(row, context);
 
     mLastLayoutWidth = getWidth();
-    mLastLayoutTime = tick_time;
+    mLayoutTimer.set(100);
     setHeight(context.y);
 }
 
@@ -507,7 +507,7 @@ void BrowserBox::maybeRelayoutText()
 {
     // Reduce relayouting frequency when there is a lot of text
     if (mTextRows.size() > 100)
-        if (mLastLayoutTime && std::abs(mLastLayoutTime - tick_time) < 10)
+        if (!mLayoutTimer.passed())
             return;
 
     relayoutText();
diff --git a/src/gui/widgets/browserbox.h b/src/gui/widgets/browserbox.h
index d7ff0428..7278bb59 100644
--- a/src/gui/widgets/browserbox.h
+++ b/src/gui/widgets/browserbox.h
@@ -23,6 +23,8 @@
 #ifndef BROWSERBOX_H
 #define BROWSERBOX_H
 
+#include "utils/time.h"
+
 #include <guichan/mouselistener.hpp>
 #include <guichan/widget.hpp>
 
@@ -193,7 +195,7 @@ class BrowserBox : public gcn::Widget,
         std::optional<BrowserLink> mHoveredLink;
         unsigned int mMaxRows = 0;
         int mLastLayoutWidth = 0;
-        int mLastLayoutTime = -1;
+        Timer mLayoutTimer;
 };
 
 #endif