Added support for a ghost block to reduce misdrops

README.md

@@ -50,12 +50,13 @@ I do not have a MacOS machine so I cannot test any builds for that OS. However,
 ## Features to add
 - ~~Create sprites for all objects~~
 - ~~Add a hold block~~
-- Add a ghost block (the outline that shows the position of the piece if dropped)
+- ~~Add a ghost block (the outline that shows the position of the piece if dropped)~~
 - Add a simple menu
 - Add basic sound effects
 ## Third party tools
 - [SDL2 framework](https://www.libsdl.org/) to handle all the low-level stuff
 - [SDL_ttf 2.0](https://www.libsdl.org/projects/SDL_ttf/) for rendering fonts
+- [SDL_image 2.0](https://www.libsdl.org/projects/SDL_image/) for loading images
 - The font I use is [Fira Sans](https://fonts.google.com/specimen/Fira+Sans)
 - [CMake scripts](https://github.com/tcbrindle/sdl2-cmake-scripts) to find SDL2, SDL_ttf, and SDL_image
 

src/config.hpp

@@ -35,12 +35,14 @@ namespace config
 
     // Constants relating to Tetris
     const int wait_time = 1000;                                     // Time in milliseconds
+    const bool ghost_piece_enabled = true;                                // Enables or disables the ghost piece to reduce misdrops
 
     // Visuals
     const SDL_Color default_text_color = {0x00, 0x00, 0x00, 0xFF};  // Default color for all text
     const Uint8 background_r_light = 0xF9;                          // Background color for light mode
     const Uint8 background_g_light = 0xE6;
     const Uint8 background_b_light = 0xCF;
+    const Uint8 transparency_alpha = 100;                           // Default alpha for transparency (with 255 being no transparency)                             
 }
 
 #endif // CONFIG_HPP

src/gamestate.cpp

@@ -67,6 +67,7 @@ void GameState::drawState ()
 {
     drawBoard();
     drawCurrentPiece(currentPiece);
+    if (!board->isGameOver() && config::ghost_piece_enabled) drawGhostPiece(currentPiece);
     if (!hold_block_first_time) drawHoldPiece(holdPiece);
     drawNextPiece(nextPiece);
 }
@@ -278,6 +279,33 @@ void GameState::drawCurrentPiece (Piece p)
     }
 }
 
+// Draws the ghost piece of the piece given
+void GameState::drawGhostPiece (Piece p)
+{
+    ghostPiece = p;
+    while (board->isPositionLegal(ghostPiece))
+    {
+        ghostPiece.r++;
+    }
+    ghostPiece.r--;
+
+    tetrominoSprites.setAlphaMode(config::transparency_alpha);  // Change transparency to render the ghost piece
+
+    for (int row = 0; row < config::matrix_blocks; row++)
+    {
+        for (int col = 0; col < config::matrix_blocks; col++)
+        {
+            if (ghostPiece.getBlockType(row, col) != 0)
+            {
+                tetrominoSprites.render(config::width_to_playfield + (col+ghostPiece.c) * config::block_size, config::height_to_playfield +
+                (row+ghostPiece.r-(config::playfield_height-config::true_playfield_height))*config::block_size, &tetrominoSpriteClips[ghostPiece.piece_type]);
+            }
+        }
+    }
+
+    tetrominoSprites.setAlphaMode(255); // Don't forget to change it back to normal!
+}
+
 void GameState::drawHoldPiece (Piece p)
 {
     for (int row = 0; row < config::matrix_blocks; row++)

src/gamestate.hpp

@@ -24,6 +24,7 @@ class GameState
     bool hold_block_used;                               // True if the hold block has been used, resets after a block is placed
     Board *board;
     Piece currentPiece {0, 0};
+    Piece ghostPiece {0, 0};
     Piece holdPiece {0, 0};
     Piece nextPiece {0, 0};
     std::queue<Piece> nextPieces;                       // Holds the next 2 pieces
@@ -34,6 +35,7 @@ class GameState
 
     void drawBoard ();
     void drawCurrentPiece (Piece p);
+    void drawGhostPiece (Piece p);
     void drawHoldPiece (Piece p);
     void drawNextPiece (Piece p);
     int getRandom (int lower_limit, int upper_limit);   // Return a random number in this range

src/texture.cpp

@@ -103,6 +103,11 @@ void Texture::renderCentered (int x, int y)
     SDL_RenderCopy(gRenderer, mTexture, nullptr, &r);
 }
 
+void Texture::setAlphaMode (Uint8 alpha)
+{
+    SDL_SetTextureAlphaMod (mTexture, alpha);
+}
+
 int Texture::getWidth()
 {
     return width;

src/texture.hpp

@@ -16,6 +16,7 @@ class Texture
     void loadFromText (std::string text, SDL_Color text_color);
     void render (int x, int y, SDL_Rect *clip = nullptr);
     void renderCentered (int x, int y);
+    void setAlphaMode (Uint8 alpha);
 
     int getWidth ();
     int getHeight ();